Getting started with the Partner Filing API

Getting started

Start with a test key

1. Create a test key as described below.
2. Choose a complete request example and supply your prepared figures.
3. Set dry_run to true and review the dry run.
4. For an approved live filing, make the submission calls below.
5. Poll each operation and check every requested return.

Use the shared partner sandbox host when sandbox access is available. Create the key on Partner API keys on that host. Send it in the Authorization header as Bearer sct_test_<secret>. Keep keys and credentials on your server. The production API accepts approved live keys only.

curl -X POST "$PARTNER_SANDBOX_URL/api/v1/filings/ct600" \
  -H 'Authorization: Bearer sct_test_<secret>' \
  -H 'Content-Type: application/json' \
  -H 'Idempotency-Key: your-stable-operation-key' \
  --data @request.json

Every response includes request_id. Preserve it for diagnostics without recording credentials. Limits are 60 requests per minute and 1,000 per day per key, plus 100 dry runs per day per Practice. A 429 response includes Retry-After in seconds. An active Practice plan and separately recorded terms, data processing agreement and release approval are required for live keys.

File with both authorities

For both authorities, prepare the two request files with their relevant credentials and make both calls:

curl -X POST https://www.simplecompanytax.co.uk/api/v1/filings/ct600 \
  -H 'Authorization: Bearer sct_live_<secret>' \
  -H 'Content-Type: application/json' -H 'Idempotency-Key: accounts-2026-hmrc' \
  --data @ct600.json
curl -X POST https://www.simplecompanytax.co.uk/api/v1/filings/accounts \
  -H 'Authorization: Bearer sct_live_<secret>' \
  -H 'Content-Type: application/json' -H 'Idempotency-Key: accounts-2026-companies-house' \
  --data @accounts.json

These live calls require approved access. Review a complete dry run first. HMRC and Companies House produce independent operation IDs and parts.