UK company lookup, filing deadlines, late penalties and Corporation Tax maths. No account.
Maintain this server? Claim it
Call this server's tools from your browser. Nothing to install.
Requests go through mcptry because browsers can't call most MCP servers directly. Header values are sent to the server for that request only and are never stored or logged.
Tool list from our last check. Connect live to refresh it.
Check whether a company fits this tool (micro-entity limits, single UK trade, no groups/R&D/gains/property). An overdrawn director loan is supported: the return carries a CT600A. Money in POUNDS.
What the customer wants to file. Only matters for periodOver12Months: a period of account over 12 months rules out a CT600 (which covers at most 12 months) but NOT a set of accounts, which Companies House takes for a period of any length up to 18 months. A first-year company normally has a period of 12 months plus a few weeks, so 'accounts' is often filable when 'ct600' is not.
Check whether a company fits this tool (micro-entity limits, single UK trade, no groups/R&D/gains/property). An overdrawn director loan is supported: the return carries a CT600A. Money in POUNDS.
| Argument | Type | Description |
|---|---|---|
| dormant | boolean | |
| turnover | number | |
| claimsRandD | boolean | |
| filingTypes | string | What the customer wants to file. Only matters for periodOver12Months: a period of account over 12 months rules out a CT600 (which covers at most 12 months) but NOT a set of accounts, which Companies House takes for a period of any length up to 18 months. A first-year company normally has a period of 12 months plus a few weeks, so 'accounts' is often filable when 'ct600' is not. |
| partOfGroup | boolean | |
| singleUkTrade | boolean | |
| averageEmployees | number | |
| balanceSheetTotal | number | |
| hasPropertyIncome | boolean | |
| hasChargeableGains | boolean | |
| periodOver12Months | boolean | |
| overdrawnDirectorsLoan | boolean |
{
"type": "object",
"properties": {
"dormant": {
"type": "boolean"
},
"turnover": {
"type": "number"
},
"claimsRandD": {
"type": "boolean"
},
"filingTypes": {
"enum": [
"ct600",
"accounts",
"both"
],
"type": "string",
"description": "What the customer wants to file. Only matters for periodOver12Months: a period of account over 12 months rules out a CT600 (which covers at most 12 months) but NOT a set of accounts, which Companies House takes for a period of any length up to 18 months. A first-year company normally has a period of 12 months plus a few weeks, so 'accounts' is often filable when 'ct600' is not."
},
"partOfGroup": {
"type": "boolean"
},
"singleUkTrade": {
"type": "boolean"
},
"averageEmployees": {
"type": "number"
},
"balanceSheetTotal": {
"type": "number"
},
"hasPropertyIncome": {
"type": "boolean"
},
"hasChargeableGains": {
"type": "boolean"
},
"periodOver12Months": {
"type": "boolean"
},
"overdrawnDirectorsLoan": {
"type": "boolean"
}
}
}Compute the corporation tax position from figures (stateless, nothing stored): tax due, taxable profit, marginal relief, losses, CT600 box values.
| Argument | Type | Description |
|---|---|---|
| figures* | object | The return figures, all in POUNDS. periodStart/periodEnd are ISO dates. |
{
"type": "object",
"required": [
"figures"
],
"properties": {
"figures": {
"type": "object",
"required": [
"periodStart",
"periodEnd"
],
"properties": {
"stocks": {
"type": "number"
},
"debtors": {
"type": "number"
},
"exporter": {
"enum": [
"goods",
"services",
"both",
"neither"
],
"type": "string",
"description": "Boxes 616-618. Did the company sell to customers outside the UK during the period? 'goods' = physical products sent abroad, 'services' = work done for overseas customers, 'both', or 'neither'. Does NOT affect the tax computation, but it is a statement of fact on a signed return, so it must be answered truthfully rather than defaulted."
},
"priorTax": {
"type": "number"
},
"turnover": {
"type": "number"
},
"periodEnd": {
"type": "string"
},
"cashAtBank": {
"type": "number"
},
"staffCosts": {
"type": "number"
},
"costOfSales": {
"type": "number"
},
"deferredTax": {
"type": "number",
"description": "Deferred tax charge (or credit) for the period. Shown with the corporation tax charge as one tax line in the accounts. Never changes what HMRC is owed."
},
"firstPeriod": {
"type": "boolean",
"description": "true = first accounting period (no comparative column)"
},
"fixedAssets": {
"type": "number"
},
"otherIncome": {
"type": "number"
},
"periodStart": {
"type": "string"
},
"priorStocks": {
"type": "number"
},
"depreciation": {
"type": "number"
},
"priorDebtors": {
"type": "number"
},
"adminExpenses": {
"type": "number",
"description": "Running costs excluding staff and depreciation"
},
"fullExpensing": {
"type": "number",
"description": "100% first-year allowance on new main-rate plant and machinery (CT600 box 688)."
},
"priorTurnover": {
"type": "number"
},
"claimCarryBack": {
"type": "boolean"
},
"interestIncome": {
"type": "number",
"description": "Bank interest received (CT600 box 170)"
},
"priorPeriodEnd": {
"type": "string"
},
"taxAlreadyPaid": {
"type": "number",
"description": "Corporation tax the company has already paid HMRC for this period and has not had back (CT600 box 595), in pounds. 0 or absent if none. Not for a period over 12 months."
},
"priorCashAtBank": {
"type": "number"
},
"priorStaffCosts": {
"type": "number"
},
"averageEmployees": {
"type": "number"
},
"priorCostOfSales": {
"type": "number"
},
"priorFixedAssets": {
"type": "number"
},
"priorOtherIncome": {
"type": "number"
},
"priorPeriodStart": {
"type": "string"
},
"tradingStartDate": {
"type": "string",
"description": "When the company started trading or first had income, ISO date. Only needed in a FIRST year whose period of account runs over 12 months (incorporation to the accounting reference date, which is the normal shape). Corporation tax starts here, not at incorporation, so a company that began trading a few weeks in usually needs only ONE CT600. The accounts still cover the whole period of account. Ask the user; do not guess."
},
"capitalAllowances": {
"type": "number",
"description": "Equipment bought this period (AIA)"
},
"mainPoolAdditions": {
"type": "number",
"description": "Main pool: expenditure added this period that AIA is not claimed on."
},
"mainPoolDisposals": {
"type": "number",
"description": "Main pool: disposal proceeds, capped at original cost. More than the pool holds produces a balancing charge."
},
"participatorLoans": {
"type": "array",
"items": {
"type": "object",
"properties": {
"name": {
"type": "string"
},
"amount": {
"type": "number"
}
}
},
"description": "CT600A Part 1: loans to directors, shareholders or their associates made in the period and still outstanding at the period end, whole pounds per person."
},
"priorDepreciation": {
"type": "number"
},
"priorOtherCharges": {
"type": "number"
},
"zeroEmissionsCars": {
"type": "number",
"description": "First-year allowance on zero-emission cars (CT600 box 726)."
},
"associatedCompanies": {
"type": "number"
},
"qualifyingDonations": {
"type": "number"
},
"disallowableExpenses": {
"type": "number",
"description": "Expenses included in the accounts that corporation tax does not allow, added back in the computation: client entertaining, fines and penalties, and similar. Do NOT subtract these from the cost figures; they stay in the accounts and are added back for tax."
},
"electricChargePoints": {
"type": "number",
"description": "100% allowance on electric vehicle charge-point equipment (CT600 box 713)."
},
"lossesBroughtForward": {
"type": "number"
},
"stubCapitalAllowances": {
"type": "number",
"description": "Only when the period of account runs over 12 months, which HMRC files as TWO returns: how much of capitalAllowances was spent in the second (stub) period. Everything else is apportioned by days, but equipment relief belongs to the period the money was actually spent. Ask the user; default 0."
},
"mainPoolBroughtForward": {
"type": "number",
"description": "Main pool: unrelieved qualifying expenditure brought forward from the previous period. Give this and we compute the writing-down allowance instead of trusting a typed one."
},
"priorYearTaxableProfit": {
"type": "number"
},
"participatorLoanReliefs": {
"type": "array",
"items": {
"type": "object",
"properties": {
"date": {
"type": "string",
"format": "date"
},
"name": {
"type": "string"
},
"repaid": {
"type": "number"
},
"writtenOff": {
"type": "number"
}
}
},
"description": "CT600A Part 2: amounts repaid, released or written off within 9 months and 1 day of the period end, with the date."
},
"stubQualifyingDonations": {
"type": "number",
"description": "As stubCapitalAllowances, for qualifyingDonations: how much was paid in the second period. Default 0."
},
"creditorsDueAfterOneYear": {
"type": "number"
},
"provisionsForLiabilities": {
"type": "number",
"description": "Deferred tax provisions, warranty claims and other future obligations. Deducted after creditors in arriving at net assets."
},
"specialRatePoolAdditions": {
"type": "number",
"description": "Special rate pool: expenditure added this period."
},
"specialRatePoolDisposals": {
"type": "number",
"description": "Special rate pool: disposal proceeds."
},
"creditorsDueWithinOneYear": {
"type": "number"
},
"machineryAndPlantMainPool": {
"type": "number",
"description": "Writing-down allowance claimed on the main pool (18%, or 14% for periods beginning on or after 1 April 2026; hybrid rate across the change)."
},
"fortyPercentFyaExpenditure": {
"type": "number",
"description": "COST of new main-rate plant and machinery bought on or after 1 January 2026 claimed under the FA 2026 40% first-year allowance; 40% is claimed this period and the remaining 60% is added to the main pool automatically (CT600 box 725 until 5 April 2027, box 696 after)."
},
"zeroEmissionsGoodsVehicles": {
"type": "number",
"description": "First-year allowance on zero-emission goods vehicles (CT600 box 723)."
},
"calledUpShareCapitalNotPaid": {
"type": "number",
"description": "Share capital called up but not yet paid by shareholders. An asset, shown before fixed assets."
},
"priorCreditorsDueAfterOneYear": {
"type": "number"
},
"priorProvisionsForLiabilities": {
"type": "number",
"description": "Provisions for liabilities last year, for the comparative column."
},
"specialRatePoolBroughtForward": {
"type": "number",
"description": "Special rate pool: balance brought forward (integral features, long-life assets, higher-emission cars)."
},
"priorCreditorsDueWithinOneYear": {
"type": "number"
},
"structuresAndBuildingsAllowance": {
"type": "number",
"description": "Structures and buildings allowance, 3% of qualifying construction cost (CT600 box 711)."
},
"machineryAndPlantSpecialRatePool": {
"type": "number",
"description": "Writing-down allowance claimed on the special rate pool (6%)."
},
"priorCalledUpShareCapitalNotPaid": {
"type": "number",
"description": "Called up share capital not paid last year, for the comparative column."
},
"participatorLoansOutstandingAllPeriods": {
"type": "number",
"description": "CT600A box A75: all loans to participators outstanding at the period end, including earlier periods."
},
"participatorLoansRepaidBeforePeriodEnd": {
"type": "boolean",
"description": "CT600A Part 1 tick box: loans made in the period and repaid before the period end."
}
},
"description": "The return figures, all in POUNDS. periodStart/periodEnd are ISO dates."
}
}
}READ THIS FIRST. How to prepare a CT600 with this server: which companies qualify, the order to gather figures in, what the words mean (micro-entity, filleted accounts, the declaration), and which cases to refer to an accountant instead. Takes no arguments.
No arguments.
{
"type": "object",
"properties": {}
}Estimate one person's UK Self Assessment for one tax year (2025-26 or 2026-27): income tax on salary, dividends, self-employment and interest, Class 4, student loans, payments on account, and Class 1 National Insurance on a salary from the person's own company. Uses the same engine as A.X.E.L Filing's returns, which matches HMRC's own test cases. An estimate only: nothing is saved or filed. Never ask for a UTR or National Insurance number.
| Argument | Type | Description |
|---|---|---|
| income | object | Income in ONE personal tax year (6 April to 5 April), all in POUNDS. Ask; do not guess. |
| region* | string | Where the person lives for income tax: rUK (England or Northern Ireland), scotland or wales. Scottish rates differ. Ask. |
| payroll | object | For the Employment Allowance (up to £10,500 of employer NI). HMRC: a company with only one director cannot claim if that director is the only employee liable for employer NI. Ask both. |
| taxYear* | string | |
| dividends | number | Total dividends received in the tax year, from any company |
| eligibility | object | Answer true for any that apply; each is refused as out of scope (refer to an accountant). |
Look up a UK company at Companies House by company number: name, status, registered office, next accounts period, and a quick fit check.
| Argument | Type | Description |
|---|---|---|
| companyNumber* | string |
{
"type": "object",
"required": [
"companyNumber"
],
"properties": {
"companyNumber": {
"type": "string"
}
}
}Late filing penalties for a UK company's accounts (Companies House) and CT600 (HMRC): what is owed if filed on a given date, and the full schedule of dates when each penalty applies. Use with lookup_uk_company, which gives the accounts deadline. Dates are ISO (YYYY-MM-DD); filedOn defaults to today.
| Argument | Type | Description |
|---|---|---|
| filedOn | string | Date the filing arrives, ISO date. Defaults to today. |
| unpaidTax | number | Corporation tax still unpaid, in POUNDS, to estimate the 10% tax-geared penalties at 6 and 12 months. |
| ct600Deadline | string | CT600 filing deadline (12 months after the end of the accounting period), ISO date |
| accountsDeadline | string | Companies House accounts deadline, ISO date |
| accountsLateLastYear | boolean | The previous year's accounts were also late: the Companies House penalty doubles. |
| ct600ThirdLateInARow | boolean | This is the third late CT600 in a row: each fixed penalty is GBP 1,000 instead of GBP 200. |
{
"type": "object",
"properties": {
"filedOn": {
"type": "string",
"description": "Date the filing arrives, ISO date. Defaults to today."
},
"unpaidTax": {
"type": "number",
"description": "Corporation tax still unpaid, in POUNDS, to estimate the 10% tax-geared penalties at 6 and 12 months."
},
"ct600Deadline": {
"type": "string",
"description": "CT600 filing deadline (12 months after the end of the accounting period), ISO date"
},
"accountsDeadline": {
"type": "string",
"description": "Companies House accounts deadline, ISO date"
},
"accountsLateLastYear": {
"type": "boolean",
"description": "The previous year's accounts were also late: the Companies House penalty doubles."
},
"ct600ThirdLateInARow": {
"type": "boolean",
"description": "This is the third late CT600 in a row: each fixed penalty is GBP 1,000 instead of GBP 200."
}
}
}The director's whole year in one view: the company's corporation tax AND the director's own Self Assessment, side by side. Give either filingId (a saved CT600 draft, signed in) or the company's figures, plus the director's salary per tax year and each dividend with the date it was PAID (dividends are taxed in the tax year paid, which may differ from the company's year). Returns the company's profit, tax and profit after tax, each personal tax year's Self Assessment, Class 1 National Insurance on the salary (employee and employer, paid through payroll, with the Employment Allowance where it applies), payments on account, every due date, and the combined total. For what-ifs, call once per scenario and compare them side by side; when a scenario changes the salary, pass figures with staffCosts adjusted (salary plus employer NI) so corporation tax reflects it (see the guide). With MORE THAN ONE company, ask about every company they draw from and pass `companies` (or, signed in, `useProfile: true` to start from their saved answers): the Self Assessment covers all of it once, associated companies share the corporation tax limits, connected companies share one Employment Allowance, and NI can add the pay together. The user decides; present options, not a recommendation. Never ask for a UTR or National Insurance number.
| Argument | Type | Description |
|---|---|---|
| figures | object | The return figures, all in POUNDS. periodStart/periodEnd are ISO dates. |
| director* | object | |
| filingId | string | A saved CT600 draft to take the company figures from (needs a signed-in account) |
| companies | array |
| postgraduateLoan |
| boolean |
| studentLoanPlans | array | Undergraduate student loan plans being repaid |
| overStatePensionAge | boolean | Over State Pension age: no employee National Insurance on salary (the company still pays employer NI) |
| becameDirectorDuringYear | boolean | Became a director part-way through the tax year. Refused: a shorter NI earnings period needs HMRC's directors' calculator. |
{
"type": "object",
"required": [
"taxYear",
"region"
],
"properties": {
"income": {
"type": "object",
"properties": {
"salary": {
"type": "number",
"description": "Salary from this company in the tax year (gross)"
},
"interest": {
"type": "number",
"description": "Bank and building society interest received"
},
"otherDividends": {
"type": "number",
"description": "Dividends from OTHER companies"
},
"selfEmployment": {
"type": "object",
"properties": {
"expenses": {
"type": "number"
},
"turnover": {
"type": "number"
}
},
"description": "A sole-trader business alongside the company, accounts for the tax year"
},
"salaryTaxDeducted": {
"type": "number",
"description": "Income tax already taken off that salary through PAYE"
},
"otherEmploymentPay": {
"type": "number",
"description": "Pay from any other job in the tax year"
},
"pensionContributions": {
"type": "number",
"description": "Personal pension contributions (gross)"
},
"otherEmploymentTaxDeducted": {
"type": "number"
}
},
"description": "Income in ONE personal tax year (6 April to 5 April), all in POUNDS. Ask; do not guess."
},
"region": {
"enum": [
"rUK",
"scotland",
"wales"
],
"type": "string",
"description": "Where the person lives for income tax: rUK (England or Northern Ireland), scotland or wales. Scottish rates differ. Ask."
},
"payroll": {
"type": "object",
"properties": {
"directors": {
"type": "number",
"description": "How many directors the company has"
},
"othersLiableForEmployerNi": {
"type": "boolean",
"description": "Is anyone else on the payroll paid more than £5,000 a year?"
}
},
"description": "For the Employment Allowance (up to £10,500 of employer NI). HMRC: a company with only one director cannot claim if that director is the only employee liable for employer NI. Ask both."
},
"taxYear": {
"enum": [
"2025-26",
"2026-27"
],
"type": "string"
},
"dividends": {
"type": "number",
"description": "Total dividends received in the tax year, from any company"
},
"eligibility": {
"type": "object",
"properties": {
"partnership": {
"type": "boolean"
},
"capitalGains": {
"type": "boolean"
},
"foreignIncome": {
"type": "boolean"
},
"ukResidentAllYear": {
"type": "boolean"
},
"childBenefitHighIncome": {
"type": "boolean"
},
"trustOrLifePolicyIncome": {
"type": "boolean"
}
},
"description": "Answer true for any that apply; each is refused as out of scope (refer to an accountant)."
},
"postgraduateLoan": {
"type": "boolean"
},
"studentLoanPlans": {
"type": "array",
"items": {
"enum": [
"plan1",
"plan2",
"plan4"
],
"type": "string"
},
"description": "Undergraduate student loan plans being repaid"
},
"overStatePensionAge": {
"type": "boolean",
"description": "Over State Pension age: no employee National Insurance on salary (the company still pays employer NI)"
},
"becameDirectorDuringYear": {
"type": "boolean",
"description": "Became a director part-way through the tax year. Refused: a shorter NI earnings period needs HMRC's directors' calculator."
}
}
}| For a person with MORE THAN ONE company: each company they draw salary or dividends from. Their Self Assessment is then worked out once on all of it, each company's corporation tax uses the associated-companies count from who controls what, connected companies share one Employment Allowance, and pay is added together for NI when businessInAssociation is true. Put the person's other income in director.years (otherDividends = companies NOT listed here) and leave director.dividends empty. |
| useProfile | boolean | Signed in only: work out the person's WHOLE position from their saved profile (their Tax cockpit): every company on their account with its latest figures, plus companies not on A.X.E.L and income from elsewhere. The result's `inputs` echoes what was used, so a what-if can pass it back as `companies` with one thing changed. |
| businessInAssociation | boolean | Do the companies share premises, staff, equipment or customers? If so HMRC adds the pay from them together for Class 1 NI (one set of thresholds). Ask when more than one company pays a salary. |
{
"type": "object",
"required": [
"director"
],
"properties": {
"figures": {
"type": "object",
"required": [
"periodStart",
"periodEnd"
],
"properties": {
"stocks": {
"type": "number"
},
"debtors": {
"type": "number"
},
"exporter": {
"enum": [
"goods",
"services",
"both",
"neither"
],
"type": "string",
"description": "Boxes 616-618. Did the company sell to customers outside the UK during the period? 'goods' = physical products sent abroad, 'services' = work done for overseas customers, 'both', or 'neither'. Does NOT affect the tax computation, but it is a statement of fact on a signed return, so it must be answered truthfully rather than defaulted."
},
"priorTax": {
"type": "number"
},
"turnover": {
"type": "number"
},
"periodEnd": {
"type": "string"
},
"cashAtBank": {
"type": "number"
},
"staffCosts": {
"type": "number"
},
"costOfSales": {
"type": "number"
},
"deferredTax": {
"type": "number",
"description": "Deferred tax charge (or credit) for the period. Shown with the corporation tax charge as one tax line in the accounts. Never changes what HMRC is owed."
},
"firstPeriod": {
"type": "boolean",
"description": "true = first accounting period (no comparative column)"
},
"fixedAssets": {
"type": "number"
},
"otherIncome": {
"type": "number"
},
"periodStart": {
"type": "string"
},
"priorStocks": {
"type": "number"
},
"depreciation": {
"type": "number"
},
"priorDebtors": {
"type": "number"
},
"adminExpenses": {
"type": "number",
"description": "Running costs excluding staff and depreciation"
},
"fullExpensing": {
"type": "number",
"description": "100% first-year allowance on new main-rate plant and machinery (CT600 box 688)."
},
"priorTurnover": {
"type": "number"
},
"claimCarryBack": {
"type": "boolean"
},
"interestIncome": {
"type": "number",
"description": "Bank interest received (CT600 box 170)"
},
"priorPeriodEnd": {
"type": "string"
},
"taxAlreadyPaid": {
"type": "number",
"description": "Corporation tax the company has already paid HMRC for this period and has not had back (CT600 box 595), in pounds. 0 or absent if none. Not for a period over 12 months."
},
"priorCashAtBank": {
"type": "number"
},
"priorStaffCosts": {
"type": "number"
},
"averageEmployees": {
"type": "number"
},
"priorCostOfSales": {
"type": "number"
},
"priorFixedAssets": {
"type": "number"
},
"priorOtherIncome": {
"type": "number"
},
"priorPeriodStart": {
"type": "string"
},
"tradingStartDate": {
"type": "string",
"description": "When the company started trading or first had income, ISO date. Only needed in a FIRST year whose period of account runs over 12 months (incorporation to the accounting reference date, which is the normal shape). Corporation tax starts here, not at incorporation, so a company that began trading a few weeks in usually needs only ONE CT600. The accounts still cover the whole period of account. Ask the user; do not guess."
},
"capitalAllowances": {
"type": "number",
"description": "Equipment bought this period (AIA)"
},
"mainPoolAdditions": {
"type": "number",
"description": "Main pool: expenditure added this period that AIA is not claimed on."
},
"mainPoolDisposals": {
"type": "number",
"description": "Main pool: disposal proceeds, capped at original cost. More than the pool holds produces a balancing charge."
},
"participatorLoans": {
"type": "array",
"items": {
"type": "object",
"properties": {
"name": {
"type": "string"
},
"amount": {
"type": "number"
}
}
},
"description": "CT600A Part 1: loans to directors, shareholders or their associates made in the period and still outstanding at the period end, whole pounds per person."
},
"priorDepreciation": {
"type": "number"
},
"priorOtherCharges": {
"type": "number"
},
"zeroEmissionsCars": {
"type": "number",
"description": "First-year allowance on zero-emission cars (CT600 box 726)."
},
"associatedCompanies": {
"type": "number"
},
"qualifyingDonations": {
"type": "number"
},
"disallowableExpenses": {
"type": "number",
"description": "Expenses included in the accounts that corporation tax does not allow, added back in the computation: client entertaining, fines and penalties, and similar. Do NOT subtract these from the cost figures; they stay in the accounts and are added back for tax."
},
"electricChargePoints": {
"type": "number",
"description": "100% allowance on electric vehicle charge-point equipment (CT600 box 713)."
},
"lossesBroughtForward": {
"type": "number"
},
"stubCapitalAllowances": {
"type": "number",
"description": "Only when the period of account runs over 12 months, which HMRC files as TWO returns: how much of capitalAllowances was spent in the second (stub) period. Everything else is apportioned by days, but equipment relief belongs to the period the money was actually spent. Ask the user; default 0."
},
"mainPoolBroughtForward": {
"type": "number",
"description": "Main pool: unrelieved qualifying expenditure brought forward from the previous period. Give this and we compute the writing-down allowance instead of trusting a typed one."
},
"priorYearTaxableProfit": {
"type": "number"
},
"participatorLoanReliefs": {
"type": "array",
"items": {
"type": "object",
"properties": {
"date": {
"type": "string",
"format": "date"
},
"name": {
"type": "string"
},
"repaid": {
"type": "number"
},
"writtenOff": {
"type": "number"
}
}
},
"description": "CT600A Part 2: amounts repaid, released or written off within 9 months and 1 day of the period end, with the date."
},
"stubQualifyingDonations": {
"type": "number",
"description": "As stubCapitalAllowances, for qualifyingDonations: how much was paid in the second period. Default 0."
},
"creditorsDueAfterOneYear": {
"type": "number"
},
"provisionsForLiabilities": {
"type": "number",
"description": "Deferred tax provisions, warranty claims and other future obligations. Deducted after creditors in arriving at net assets."
},
"specialRatePoolAdditions": {
"type": "number",
"description": "Special rate pool: expenditure added this period."
},
"specialRatePoolDisposals": {
"type": "number",
"description": "Special rate pool: disposal proceeds."
},
"creditorsDueWithinOneYear": {
"type": "number"
},
"machineryAndPlantMainPool": {
"type": "number",
"description": "Writing-down allowance claimed on the main pool (18%, or 14% for periods beginning on or after 1 April 2026; hybrid rate across the change)."
},
"fortyPercentFyaExpenditure": {
"type": "number",
"description": "COST of new main-rate plant and machinery bought on or after 1 January 2026 claimed under the FA 2026 40% first-year allowance; 40% is claimed this period and the remaining 60% is added to the main pool automatically (CT600 box 725 until 5 April 2027, box 696 after)."
},
"zeroEmissionsGoodsVehicles": {
"type": "number",
"description": "First-year allowance on zero-emission goods vehicles (CT600 box 723)."
},
"calledUpShareCapitalNotPaid": {
"type": "number",
"description": "Share capital called up but not yet paid by shareholders. An asset, shown before fixed assets."
},
"priorCreditorsDueAfterOneYear": {
"type": "number"
},
"priorProvisionsForLiabilities": {
"type": "number",
"description": "Provisions for liabilities last year, for the comparative column."
},
"specialRatePoolBroughtForward": {
"type": "number",
"description": "Special rate pool: balance brought forward (integral features, long-life assets, higher-emission cars)."
},
"priorCreditorsDueWithinOneYear": {
"type": "number"
},
"structuresAndBuildingsAllowance": {
"type": "number",
"description": "Structures and buildings allowance, 3% of qualifying construction cost (CT600 box 711)."
},
"machineryAndPlantSpecialRatePool": {
"type": "number",
"description": "Writing-down allowance claimed on the special rate pool (6%)."
},
"priorCalledUpShareCapitalNotPaid": {
"type": "number",
"description": "Called up share capital not paid last year, for the comparative column."
},
"participatorLoansOutstandingAllPeriods": {
"type": "number",
"description": "CT600A box A75: all loans to participators outstanding at the period end, including earlier periods."
},
"participatorLoansRepaidBeforePeriodEnd": {
"type": "boolean",
"description": "CT600A Part 1 tick box: loans made in the period and repaid before the period end."
}
},
"description": "The return figures, all in POUNDS. periodStart/periodEnd are ISO dates."
},
"director": {
"type": "object",
"required": [
"region"
],
"properties": {
"years": {
"type": "object",
"properties": {
"2025-26": {
"type": "object",
"properties": {
"salary": {
"type": "number",
"description": "Salary from this company in the tax year (gross)"
},
"interest": {
"type": "number",
"description": "Bank and building society interest received"
},
"otherDividends": {
"type": "number",
"description": "Dividends from OTHER companies"
},
"selfEmployment": {
"type": "object",
"properties": {
"expenses": {
"type": "number"
},
"turnover": {
"type": "number"
}
},
"description": "A sole-trader business alongside the company, accounts for the tax year"
},
"salaryTaxDeducted": {
"type": "number",
"description": "Income tax already taken off that salary through PAYE"
},
"otherEmploymentPay": {
"type": "number",
"description": "Pay from any other job in the tax year"
},
"pensionContributions": {
"type": "number",
"description": "Personal pension contributions (gross)"
},
"otherEmploymentTaxDeducted": {
"type": "number"
}
},
"description": "Income in ONE personal tax year (6 April to 5 April), all in POUNDS. Ask; do not guess."
},
"2026-27": {
"type": "object",
"properties": {
"salary": {
"type": "number",
"description": "Salary from this company in the tax year (gross)"
},
"interest": {
"type": "number",
"description": "Bank and building society interest received"
},
"otherDividends": {
"type": "number",
"description": "Dividends from OTHER companies"
},
"selfEmployment": {
"type": "object",
"properties": {
"expenses": {
"type": "number"
},
"turnover": {
"type": "number"
}
},
"description": "A sole-trader business alongside the company, accounts for the tax year"
},
"salaryTaxDeducted": {
"type": "number",
"description": "Income tax already taken off that salary through PAYE"
},
"otherEmploymentPay": {
"type": "number",
"description": "Pay from any other job in the tax year"
},
"pensionContributions": {
"type": "number",
"description": "Personal pension contributions (gross)"
},
"otherEmploymentTaxDeducted": {
"type": "number"
}
},
"description": "Income in ONE personal tax year (6 April to 5 April), all in POUNDS. Ask; do not guess."
}
},
"description": "Income per personal tax year, keyed '2025-26' / '2026-27'"
},
"region": {
"enum": [
"rUK",
"scotland",
"wales"
],
"type": "string",
"description": "Where the person lives for income tax: rUK (England or Northern Ireland), scotland or wales. Scottish rates differ. Ask."
},
"payroll": {
"type": "object",
"properties": {
"directors": {
"type": "number",
"description": "How many directors the company has"
},
"othersLiableForEmployerNi": {
"type": "boolean",
"description": "Is anyone else on the payroll paid more than £5,000 a year?"
}
},
"description": "For the Employment Allowance (up to £10,500 of employer NI). HMRC: a company with only one director cannot claim if that director is the only employee liable for employer NI. Ask both."
},
"dividends": {
"type": "array",
"items": {
"type": "object",
"required": [
"date",
"amount"
],
"properties": {
"date": {
"type": "string",
"description": "YYYY-MM-DD"
},
"amount": {
"type": "number"
}
}
},
"description": "Each dividend from this company with the date it was paid"
},
"eligibility": {
"type": "object",
"properties": {
"partnership": {
"type": "boolean"
},
"capitalGains": {
"type": "boolean"
},
"foreignIncome": {
"type": "boolean"
},
"ukResidentAllYear": {
"type": "boolean"
},
"childBenefitHighIncome": {
"type": "boolean"
},
"trustOrLifePolicyIncome": {
"type": "boolean"
}
},
"description": "Answer true for any that apply; each is refused as out of scope (refer to an accountant)."
},
"postgraduateLoan": {
"type": "boolean"
},
"studentLoanPlans": {
"type": "array",
"items": {
"enum": [
"plan1",
"plan2",
"plan4"
],
"type": "string"
},
"description": "Undergraduate student loan plans being repaid"
},
"overStatePensionAge": {
"type": "boolean",
"description": "Over State Pension age: no employee National Insurance on salary (the company still pays employer NI)"
},
"becameDirectorDuringYear": {
"type": "boolean",
"description": "Became a director part-way through the tax year. Refused: a shorter NI earnings period needs HMRC's directors' calculator."
}
}
},
"filingId": {
"type": "string",
"description": "A saved CT600 draft to take the company figures from (needs a signed-in account)"
},
"companies": {
"type": "array",
"items": {
"type": "object",
"required": [
"name"
],
"properties": {
"name": {
"type": "string"
},
"control": {
"enum": [
"me",
"jointly",
"no"
],
"type": "string",
"description": "Who controls it (over half the shares or votes): 'me' on their own, 'jointly' with others such as a partner (treated as the same group of people for each such company), 'no' not them. Companies with the same control are associated and connected. Ask."
},
"dormant": {
"type": "boolean",
"description": "No trade or business at all in the period: never counts as associated"
},
"figures": {
"type": "object",
"required": [
"periodStart",
"periodEnd"
],
"properties": {
"stocks": {
"type": "number"
},
"debtors": {
"type": "number"
},
"exporter": {
"enum": [
"goods",
"services",
"both",
"neither"
],
"type": "string",
"description": "Boxes 616-618. Did the company sell to customers outside the UK during the period? 'goods' = physical products sent abroad, 'services' = work done for overseas customers, 'both', or 'neither'. Does NOT affect the tax computation, but it is a statement of fact on a signed return, so it must be answered truthfully rather than defaulted."
},
"priorTax": {
"type": "number"
},
"turnover": {
"type": "number"
},
"periodEnd": {
"type": "string"
},
"cashAtBank": {
"type": "number"
},
"staffCosts": {
"type": "number"
},
"costOfSales": {
"type": "number"
},
"deferredTax": {
"type": "number",
"description": "Deferred tax charge (or credit) for the period. Shown with the corporation tax charge as one tax line in the accounts. Never changes what HMRC is owed."
},
"firstPeriod": {
"type": "boolean",
"description": "true = first accounting period (no comparative column)"
},
"fixedAssets": {
"type": "number"
},
"otherIncome": {
"type": "number"
},
"periodStart": {
"type": "string"
},
"priorStocks": {
"type": "number"
},
"depreciation": {
"type": "number"
},
"priorDebtors": {
"type": "number"
},
"adminExpenses": {
"type": "number",
"description": "Running costs excluding staff and depreciation"
},
"fullExpensing": {
"type": "number",
"description": "100% first-year allowance on new main-rate plant and machinery (CT600 box 688)."
},
"priorTurnover": {
"type": "number"
},
"claimCarryBack": {
"type": "boolean"
},
"interestIncome": {
"type": "number",
"description": "Bank interest received (CT600 box 170)"
},
"priorPeriodEnd": {
"type": "string"
},
"taxAlreadyPaid": {
"type": "number",
"description": "Corporation tax the company has already paid HMRC for this period and has not had back (CT600 box 595), in pounds. 0 or absent if none. Not for a period over 12 months."
},
"priorCashAtBank": {
"type": "number"
},
"priorStaffCosts": {
"type": "number"
},
"averageEmployees": {
"type": "number"
},
"priorCostOfSales": {
"type": "number"
},
"priorFixedAssets": {
"type": "number"
},
"priorOtherIncome": {
"type": "number"
},
"priorPeriodStart": {
"type": "string"
},
"tradingStartDate": {
"type": "string",
"description": "When the company started trading or first had income, ISO date. Only needed in a FIRST year whose period of account runs over 12 months (incorporation to the accounting reference date, which is the normal shape). Corporation tax starts here, not at incorporation, so a company that began trading a few weeks in usually needs only ONE CT600. The accounts still cover the whole period of account. Ask the user; do not guess."
},
"capitalAllowances": {
"type": "number",
"description": "Equipment bought this period (AIA)"
},
"mainPoolAdditions": {
"type": "number",
"description": "Main pool: expenditure added this period that AIA is not claimed on."
},
"mainPoolDisposals": {
"type": "number",
"description": "Main pool: disposal proceeds, capped at original cost. More than the pool holds produces a balancing charge."
},
"participatorLoans": {
"type": "array",
"items": {
"type": "object",
"properties": {
"name": {
"type": "string"
},
"amount": {
"type": "number"
}
}
},
"description": "CT600A Part 1: loans to directors, shareholders or their associates made in the period and still outstanding at the period end, whole pounds per person."
},
"priorDepreciation": {
"type": "number"
},
"priorOtherCharges": {
"type": "number"
},
"zeroEmissionsCars": {
"type": "number",
"description": "First-year allowance on zero-emission cars (CT600 box 726)."
},
"associatedCompanies": {
"type": "number"
},
"qualifyingDonations": {
"type": "number"
},
"disallowableExpenses": {
"type": "number",
"description": "Expenses included in the accounts that corporation tax does not allow, added back in the computation: client entertaining, fines and penalties, and similar. Do NOT subtract these from the cost figures; they stay in the accounts and are added back for tax."
},
"electricChargePoints": {
"type": "number",
"description": "100% allowance on electric vehicle charge-point equipment (CT600 box 713)."
},
"lossesBroughtForward": {
"type": "number"
},
"stubCapitalAllowances": {
"type": "number",
"description": "Only when the period of account runs over 12 months, which HMRC files as TWO returns: how much of capitalAllowances was spent in the second (stub) period. Everything else is apportioned by days, but equipment relief belongs to the period the money was actually spent. Ask the user; default 0."
},
"mainPoolBroughtForward": {
"type": "number",
"description": "Main pool: unrelieved qualifying expenditure brought forward from the previous period. Give this and we compute the writing-down allowance instead of trusting a typed one."
},
"priorYearTaxableProfit": {
"type": "number"
},
"participatorLoanReliefs": {
"type": "array",
"items": {
"type": "object",
"properties": {
"date": {
"type": "string",
"format": "date"
},
"name": {
"type": "string"
},
"repaid": {
"type": "number"
},
"writtenOff": {
"type": "number"
}
}
},
"description": "CT600A Part 2: amounts repaid, released or written off within 9 months and 1 day of the period end, with the date."
},
"stubQualifyingDonations": {
"type": "number",
"description": "As stubCapitalAllowances, for qualifyingDonations: how much was paid in the second period. Default 0."
},
"creditorsDueAfterOneYear": {
"type": "number"
},
"provisionsForLiabilities": {
"type": "number",
"description": "Deferred tax provisions, warranty claims and other future obligations. Deducted after creditors in arriving at net assets."
},
"specialRatePoolAdditions": {
"type": "number",
"description": "Special rate pool: expenditure added this period."
},
"specialRatePoolDisposals": {
"type": "number",
"description": "Special rate pool: disposal proceeds."
},
"creditorsDueWithinOneYear": {
"type": "number"
},
"machineryAndPlantMainPool": {
"type": "number",
"description": "Writing-down allowance claimed on the main pool (18%, or 14% for periods beginning on or after 1 April 2026; hybrid rate across the change)."
},
"fortyPercentFyaExpenditure": {
"type": "number",
"description": "COST of new main-rate plant and machinery bought on or after 1 January 2026 claimed under the FA 2026 40% first-year allowance; 40% is claimed this period and the remaining 60% is added to the main pool automatically (CT600 box 725 until 5 April 2027, box 696 after)."
},
"zeroEmissionsGoodsVehicles": {
"type": "number",
"description": "First-year allowance on zero-emission goods vehicles (CT600 box 723)."
},
"calledUpShareCapitalNotPaid": {
"type": "number",
"description": "Share capital called up but not yet paid by shareholders. An asset, shown before fixed assets."
},
"priorCreditorsDueAfterOneYear": {
"type": "number"
},
"priorProvisionsForLiabilities": {
"type": "number",
"description": "Provisions for liabilities last year, for the comparative column."
},
"specialRatePoolBroughtForward": {
"type": "number",
"description": "Special rate pool: balance brought forward (integral features, long-life assets, higher-emission cars)."
},
"priorCreditorsDueWithinOneYear": {
"type": "number"
},
"structuresAndBuildingsAllowance": {
"type": "number",
"description": "Structures and buildings allowance, 3% of qualifying construction cost (CT600 box 711)."
},
"machineryAndPlantSpecialRatePool": {
"type": "number",
"description": "Writing-down allowance claimed on the special rate pool (6%)."
},
"priorCalledUpShareCapitalNotPaid": {
"type": "number",
"description": "Called up share capital not paid last year, for the comparative column."
},
"participatorLoansOutstandingAllPeriods": {
"type": "number",
"description": "CT600A box A75: all loans to participators outstanding at the period end, including earlier periods."
},
"participatorLoansRepaidBeforePeriodEnd": {
"type": "boolean",
"description": "CT600A Part 1 tick box: loans made in the period and repaid before the period end."
}
},
"description": "The company year's figures, if known; omit for a company whose accounts you do not have (no corporation tax side)"
},
"payroll": {
"type": "object",
"properties": {
"directors": {
"type": "number"
},
"othersLiableForEmployerNi": {
"type": "boolean"
}
}
},
"filingId": {
"type": "string",
"description": "Signed in: take this company's figures from a saved CT600 draft instead"
},
"salaries": {
"type": "object",
"description": "Salary from this company per tax year, keyed '2025-26' / '2026-27': { salary, taxDeducted }"
},
"dividends": {
"type": "array",
"items": {
"type": "object",
"required": [
"date",
"amount"
],
"properties": {
"date": {
"type": "string",
"description": "YYYY-MM-DD, the date PAID"
},
"amount": {
"type": "number"
}
}
}
}
}
},
"description": "For a person with MORE THAN ONE company: each company they draw salary or dividends from. Their Self Assessment is then worked out once on all of it, each company's corporation tax uses the associated-companies count from who controls what, connected companies share one Employment Allowance, and pay is added together for NI when businessInAssociation is true. Put the person's other income in director.years (otherDividends = companies NOT listed here) and leave director.dividends empty."
},
"useProfile": {
"type": "boolean",
"description": "Signed in only: work out the person's WHOLE position from their saved profile (their Tax cockpit): every company on their account with its latest figures, plus companies not on A.X.E.L and income from elsewhere. The result's `inputs` echoes what was used, so a what-if can pass it back as `companies` with one thing changed."
},
"businessInAssociation": {
"type": "boolean",
"description": "Do the companies share premises, staff, equipment or customers? If so HMRC adds the pay from them together for Class 1 NI (one set of thresholds). Ask when more than one company pays a salary."
}
}
}