{"openapi":"3.1.0","info":{"title":"UK Corporation Tax Calculator API","version":"0.1.0","description":"UK Corporation Tax Calculator estimates the Corporation Tax of a UK company for one accounting period from the taxable profits you supply. corp_tax_estimate applies the 19% small profits rate up to GBP 50,000, the 25% main rate above GBP 250,000 and marginal relief in between using the HMRC formula (fraction 3/200 times the upper limit less augmented profits, times taxable profits over augmented...\n\nEvery operation is read-only or compute-only. The same tools are available over MCP (streamable HTTP) at https://uk-corp-tax-calc.connectorbay.com/mcp.\n\nDisclaimer: General information only, not legal, tax, accounting or payment advice. UK Corporation Tax Calculator is an independent tool: it is not affiliated with, endorsed by or operated by any government body, central bank, standards body or scheme operator. Rates, thresholds and rules change; check the cited official source and confirm with a qualified professional before you rely on a result.","contact":{"name":"Unify Dynamics LLC","email":"agent@connectorbay.com","url":"https://connectorbay.com/uk-corp-tax-calc/docs"},"termsOfService":"https://connectorbay.com/uk-corp-tax-calc/terms"},"servers":[{"url":"https://uk-corp-tax-calc.connectorbay.com"}],"externalDocs":{"url":"https://connectorbay.com/uk-corp-tax-calc/docs"},"security":[{},{"bearer":[]}],"components":{"securitySchemes":{"bearer":{"type":"http","scheme":"bearer","description":"Optional. A Pro API key raises rate limits; no credentials are required."}},"schemas":{"Error":{"type":"object","properties":{"ok":{"const":false},"error":{"type":"object"}}}}},"paths":{"/v1/tools/corp_tax_estimate":{"post":{"operationId":"corp_tax_estimate","summary":"Estimate Corporation Tax for one accounting period using the 19% small profits rate, the 25% main rate and marginal reli","description":"Estimate Corporation Tax for one accounting period using the 19% small profits rate, the 25% main rate and marginal relief between the limits. Use for \"My company made GBP 90,000 profit in the year to 30 September 2026: how much Corporation Tax is that?\".","tags":["tools"],"requestBody":{"required":true,"content":{"application/json":{"schema":{"properties":{"taxable_profits":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"description":"Taxable total profits of the accounting period in GBP as a plain decimal string such as 90000 (enter 0 for a loss).","title":"Taxable Profits"},"period_start":{"description":"First day of the accounting period, YYYY-MM-DD (on or after 2023-04-01).","title":"Period Start","type":"string"},"period_end":{"description":"Last day of the accounting period, YYYY-MM-DD (at most 12 months after the start).","title":"Period End","type":"string"},"associated_companies":{"default":0,"description":"Number of OTHER companies associated with this one (0 if none); the limits are divided by 1 plus this number.","maximum":1000,"minimum":0,"title":"Associated Companies","type":"integer"},"exempt_distributions":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"default":"0","description":"Exempt distributions received from companies outside the group, in GBP (they count towards augmented profits for the limits). 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Use for \"How mu","description":"Return the marginal relief in the band between the lower and upper profits limits, with the limits used. Use for \"How much marginal relief do I get on GBP 120,000 of profit?\".","tags":["tools"],"requestBody":{"required":true,"content":{"application/json":{"schema":{"properties":{"taxable_profits":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"description":"Taxable total profits of the accounting period in GBP as a plain decimal string such as 90000 (enter 0 for a loss).","title":"Taxable Profits"},"period_start":{"description":"First day of the accounting period, YYYY-MM-DD (on or after 2023-04-01).","title":"Period Start","type":"string"},"period_end":{"description":"Last day of the accounting period, YYYY-MM-DD (at most 12 months after the start).","title":"Period End","type":"string"},"associated_companies":{"default":0,"description":"Number of OTHER companies associated with this one (0 if none); the limits are divided by 1 plus this number.","maximum":1000,"minimum":0,"title":"Associated Companies","type":"integer"},"exempt_distributions":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"default":"0","description":"Exempt distributions received from companies outside the group, in GBP (they count towards augmented profits for the limits). 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Use for \"What is my effective Corporation Tax rate on GBP 180,000 of profit?\".","tags":["tools"],"requestBody":{"required":true,"content":{"application/json":{"schema":{"properties":{"taxable_profits":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"description":"Taxable total profits of the accounting period in GBP as a plain decimal string such as 90000 (enter 0 for a loss).","title":"Taxable Profits"},"period_start":{"description":"First day of the accounting period, YYYY-MM-DD (on or after 2023-04-01).","title":"Period Start","type":"string"},"period_end":{"description":"Last day of the accounting period, YYYY-MM-DD (at most 12 months after the start).","title":"Period End","type":"string"},"associated_companies":{"default":0,"description":"Number of OTHER companies associated with this one (0 if none); the limits are divided by 1 plus this number.","maximum":1000,"minimum":0,"title":"Associated Companies","type":"integer"},"exempt_distributions":{"anyOf":[{"type":"string"},{"type":"integer"},{"type":"number"}],"default":"0","description":"Exempt distributions received from companies outside the group, in GBP (they count towards augmented profits for the limits). 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Use for \"I have two other companies under the same owner: how do the Corporation Tax limits change?\".","tags":["tools"],"requestBody":{"required":true,"content":{"application/json":{"schema":{"properties":{"associated_companies":{"description":"Number of OTHER companies associated with this one (0 if none); the limits are divided by 1 plus this number.","maximum":1000,"minimum":0,"title":"Associated Companies","type":"integer"}},"required":["associated_companies"],"title":"associated_companies_adjustmentArguments","type":"object"}}}},"responses":{"200":{"description":"Tool result. `ok: true` on success; `ok: false` with a structured `error` (provider_unavailable, upstream_error, bad_input) when the tool could not answer.","content":{"application/json":{"schema":{"type":"object","additionalProperties":true}}}},"422":{"description":"Arguments failed validation","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}},"429":{"description":"Rate limit exceeded (see Retry-After)","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}},"x-read-only":true}},"/v1/tools/short_period_adjustment":{"post":{"operationId":"short_period_adjustment","summary":"Return the marginal relief limits for an accounting period shorter than 12 months (days divided by 365). 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Use for \"Our first accounting period runs 1 January to 31 March: how are the Corporation Tax limits reduced?\".","tags":["tools"],"requestBody":{"required":true,"content":{"application/json":{"schema":{"properties":{"period_start":{"description":"First day of the accounting period, YYYY-MM-DD (on or after 2023-04-01).","title":"Period Start","type":"string"},"period_end":{"description":"Last day of the accounting period, YYYY-MM-DD (at most 12 months after the start).","title":"Period End","type":"string"},"associated_companies":{"default":0,"description":"Number of OTHER companies associated with this one (0 if none); the limits are divided by 1 plus this number.","maximum":1000,"minimum":0,"title":"Associated Companies","type":"integer"}},"required":["period_start","period_end"],"title":"short_period_adjustmentArguments","type":"object"}}}},"responses":{"200":{"description":"Tool result. `ok: true` on success; `ok: false` with a structured `error` (provider_unavailable, upstream_error, bad_input) when the tool could not answer.","content":{"application/json":{"schema":{"type":"object","additionalProperties":true}}}},"422":{"description":"Arguments failed validation","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}},"429":{"description":"Rate limit exceeded (see Retry-After)","content":{"application/json":{"schema":{"$ref":"#/components/schemas/Error"}}}}},"x-read-only":true}},"/v1/tools/company_deadlines":{"post":{"operationId":"company_deadlines","summary":"Return the Corporation Tax payment date (9 months and one day after the period end) and the Company Tax Return date (12 ","description":"Return the Corporation Tax payment date (9 months and one day after the period end) and the Company Tax Return date (12 months after). 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