API reference

Complete reference for every Render endpoint, parameter, and response field.

Base URL

text

https://api.render.my

All endpoints are served over HTTPS only. HTTP requests are not accepted. All request and response bodies use application/json.

Authentication

Render uses API keys to authenticate requests. Pass your key as a Bearer token in the Authorization header:

bash

Authorization: Bearer sk_sandbox_your_key_here

Sandbox keys (sk_sandbox_) route to the Render sandbox — never HMRC. Live keys (sk_live_) route to HMRC production. No other configuration is needed to switch environments.

API keys are generated in your dashboard. Keep them secret — never commit them to source control. Use environment variables.

Create a filing

POST/v1/filingsSubmit a CT600 return

Submits a CT600 corporation tax return to HMRC. Returns a Filing object.

Request parameters

Parameter	Type	Description
`company`required	`object`	Company identification details.
`company.name`required	`string`	Registered company name.
`company.utr`required	`string`	10-digit Unique Taxpayer Reference.
`company.registration_number`required	`string`	Companies House registration number (8 digits).
`period`required	`object`	Accounting period dates.
`period.start`required	`string`	Period start date (ISO 8601: YYYY-MM-DD).
`period.end`required	`string`	Period end date (ISO 8601: YYYY-MM-DD).
`financials`required	`object`	Financial figures. All monetary values are integers in pence.
`financials.turnover`required	`integer`	Total turnover for the period, in pence (CT600 Box 145).
`financials.trading_profit`required	`integer`	Trading profit for the period, in pence (CT600 Box 37). Pass 0 for a nil return.
`financials.gross_profit`	`integer`	Gross profit in pence (CT600 Box 150). Defaults to 0.
`financials.net_profit`	`integer`	Net profit in pence (CT600 Box 155). Defaults to 0.
`financials.tax_rate_year`	`integer`	Financial year for the applicable tax rate (e.g. 2025). Defaults to current year.
`accounts`	`object`	iXBRL accounts attachment options.
`accounts.standard`	`string`	"frs102" (small companies) or "frs105" (micro-entities). Defaults to "frs102".
`accounts.ixbrl`	`string`	Base64-encoded iXBRL document. If omitted, Render generates a minimal iXBRL from your financials.
`options`	`object`	Submission options.
`options.idempotency_key`	`string`	Idempotency key. Equivalent to passing the Idempotency-Key header.
`options.test_mode`	`boolean`	If true and a live key is used, routes to HMRC Test-in-Live rather than production. Defaults to false.

Example request

cURL

curl https://api.render.my/v1/filings \
  -H "Authorization: Bearer sk_sandbox_..." \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: my-unique-key-123" \
  -d '{
    "company": {
      "name": "Acme Ltd",
      "utr": "1234567890",
      "registration_number": "12345678"
    },
    "period": {
      "start": "2024-04-01",
      "end": "2025-03-31"
    },
    "financials": {
      "turnover": 9000000,
      "trading_profit": 1200000,
      "tax_rate_year": 2025
    },
    "accounts": { "standard": "frs102" }
  }'

Retrieve a filing

GET/v1/filings/:idGet filing status

Returns the current state of a filing, including HMRC acknowledgement status.

cURL

curl https://api.render.my/v1/filings/fil_1a2b3c4d5e6f \
  -H "Authorization: Bearer sk_sandbox_..."

Amend a filing

POST/v1/filings/:id/amendSubmit an amendment

Submits an amendment to a previously filed return. The engine sets the GovTalk qualifier to amendment and recalculates the IRmark automatically.

cURL

curl https://api.render.my/v1/filings/fil_1a2b3c4d5e6f/amend \
  -H "Authorization: Bearer sk_sandbox_..." \
  -H "Content-Type: application/json" \
  -d '{
    "financials": {
      "trading_profit": 13000000
    }
  }'

Validate without submitting

POST/v1/validatePre-submission validation

Validates a return against the HMRC schema and BVR schematron rules without submitting. Returns a list of errors, or an empty errors array if the return is valid.

Response — valid

{
  "valid": true,
  "errors": []
}

Response — invalid

{
  "valid": false,
  "errors": [
    {
      "code": "invalid_utr",
      "message": "UTR must be exactly 10 digits.",
      "field": "company.utr"
    }
  ]
}

The Filing object

Parameter	Type	Description
`id`	`string`	Filing ID. Always starts with "fil_".
`object`	`string`	Always "filing".
`status`	`string`	"pending" \| "submitted" \| "acknowledged" \| "failed".
`correlation_id`	`string \| null`	HMRC CorrelationID returned after submission. Null until HMRC accepts the submission.
`company_utr`	`string`	10-digit UTR of the filing company.
`period_start`	`string`	Accounting period start date (YYYY-MM-DD).
`period_end`	`string`	Accounting period end date (YYYY-MM-DD).
`tax_due_pence`	`integer \| null`	Estimated CT in pence, computed from the figures you supplied. Not a final HMRC determination — HMRC confirms liability on acknowledgement.
`submitted_at`	`string \| null`	ISO 8601 timestamp when the filing was submitted to HMRC.
`acknowledged_at`	`string \| null`	ISO 8601 timestamp when HMRC acknowledged the filing. Null until acknowledged.
`livemode`	`boolean`	true if submitted with a live key; false for sandbox.