The Quarterwise API

What you can do with it

The API covers the transaction ledger: list your income sources (UK property, overseas property and self-employment), look up the valid HMRC category keys for each, read transactions back, and write new ones in bulk. Writes are idempotent on your own reference ids, so a retried import never double-counts income. Anything you post without a category lands in the normal review queue in the app.

curl -X POST https://quarterwise.co.uk/api/v1/sources/SOURCE_ID/transactions \
  -H "Authorization: Bearer qw_live_..." \
  -H "Content-Type: application/json" \
  -d '{"date":"2026-05-01","type":"income","amountPence":95000,
       "category":"periodAmount","externalRef":"may-rent-2026"}'

Getting a key

Keys are created in the app under Account, then API access, and belong to the Pro plan. Each key is shown once at creation; we store only a hash of it, and you can revoke a key at any time with immediate effect. Send it as a bearer token on every request. Limits are generous for bookkeeping use: 120 requests a minute per key, and up to 500 transactions per write.

What it deliberately does not do

The API never submits anything to HMRC. A tax return carries a legal declaration that the figures are correct and complete, and that declaration is made by you, in the app, with the figures in front of you. The API also cannot create or delete properties or businesses, upload receipts, or run tax calculations. It gets your bookkeeping data in; the app does the rest.

Building an integration with an AI agent or a code generator? The full reference is also served as plain markdown at /developers/docs.md and as OpenAPI 3.1 at /api/v1/openapi.json.