Power your own tax calculator

This is the lightest way to build on OpenAccountants: take only the data. If you're a neobank or invoicing tool building your own in-house tax calculator, you want accurate, cited inputs — local rates and allowances — and you'll do the computation yourself.

1. Fetch the rules for a jurisdiction

One anonymous request returns every published rule as markdown:

curl https://www.openaccountants.com/api/bundle/US-CA

No auth, no key. The {jurisdiction} segment takes an ISO code (US-CA, GB, MT) or a country name (malta). See the HTTP API reference for headers and caching.

2. Parse what you need

Each rule is cited to its source, and its quality tier travels with it — Q1 (accountant-verified) or Q2 (source-cited draft). Pull the figures you care about (brackets, thresholds, allowances, deadlines) into your own model. A common pattern:

fetch bundle  →  extract the figures + their tier + source link
              →  store them with an "as of" date
              →  refresh when your cache (≈1h) expires

Surface the tier and the source link in your own UI where it matters — a user (or your compliance team) should be able to see whether a number is accountant-verified and where it came from.

3. Do the maths

The bundle gives you the inputs, not a computed answer. You apply them to the user's numbers in your own engine. That's the trade-off of the data-only path: maximum control, and you own the calculation.

When to reach for more

• Want the reasoning done for you — estimates, set-asides, deduction detection? That's the MCP intelligence tools.
• Want a credentialed human to review and sign before a user files? That's accountant handoff.

This guide is block one of the three composable building blocks on /for-platforms — take just the data, or combine it with the others.