Last updated 9 October 2026View as Markdown

Limits

Each plan sets how many calculations it includes a month and how many calls a second each key can make. Every plan has every endpoint and every tax year.

By plan

Plan	Included a month	Beyond that	Calls a second, per key
Free	100 calculations a month	Stops until next month (402, with an upgrade link)	5 a second
Pro	5,000 calculations a month	£4 per 1,000 more	20 a second
Scale	50,000 calculations a month	£2 per 1,000 more	50 a second
Enterprise	Your volume	Agreed with you	Agreed, with an SLA

Months are calendar months in UTC: the free allowance starts again on the 1st. Prices and plans are on pricing.

What counts

One successful call (a 200) to an endpoint that needs a key is one calculation, whichever endpoint it is.
A call refused for bad input, a missing or wrong key, or a limit isn’t counted.
Reference data (/v1/tax-years, /v1/rates, /v1/tax-codes/{code}) needs no key and is never counted.
Every call made with a key, counted or not, is in your dashboard’s call log with its X-Request-Id, except those refused for going over the calls a second.

At the limit

On Free, once the month’s 100 are used, calls get 402 QUOTA_EXCEEDED until the 1st. The error’s upgrade_url is where to choose a plan with more.
Paid plans keep working past their included calculations; the extra are charged as pricing says.
More calls a second with one key than the plan allows get 429 RATE_LIMITED, with Retry-After in seconds.
We email you when the month reaches 80% and 100% of what your plan includes.

402 Payment Required

{
  "error": {
    "code": "QUOTA_EXCEEDED",
    "message": "Your free plan's 100 calculations for this month are used. They start again on 1 November 2026, or choose a plan with more.",
    "upgrade_url": "https://checktakehomepay.co.uk/app/billing"
  }
}

Headers

Header	What it says
`X-Quota-Limit`	The calculations your plan includes this month.
`X-Quota-Remaining`	How many of them are left, after this call.
`X-RateLimit-Limit`	Calls a second allowed with this key.
`X-RateLimit-Remaining`	How many more this second.
`Retry-After`	With a 429: seconds to wait.
`X-Request-Id`	This call’s id, as your call log shows it. Quote it when you ask us about a call.