Best Exchange Rate API for the UK in 2026: 8 Compared for GBP Rates, HMRC and Bank of England Data

A UK business that invoices or buys in foreign currency deals with two rate questions. What is the pound worth right now, for pricing? And what rate will HMRC accept on the VAT return and the customs declaration? The second has a specific answer, and it is not the number most currency APIs return.

This comparison looks at eight exchange rate APIs from the point of view of a team in the UK. Free-tier limits and prices were read from each provider's own pricing page on 10 November 2026; they change often, so confirm before you commit.

What a team in the UK needs from an exchange rate API

• Live GBP pairs for pricing and checkout.
• HMRC monthly exchange rates, the period rates published for customs and VAT.
• HMRC spot and average rates, published as at 31 March and 31 December.
• Bank of England daily spot rates against sterling, widely used for accounting.
• History by date for invoices and year-end.

Quick comparison

The UK rates and what they are for

• HMRC monthly rates. HMRC publishes them on the penultimate Thursday of each month for the following calendar month, as CSV and XML. They are the period rates for customs and VAT.
• VAT Notice 700, section 7.6. For a supply in foreign currency you must use the UK market selling rate at the time of the supply, or you may use the period rate of exchange published by HMRC for customs purposes. Any other rate needs a written application to HMRC.
• HMRC spot and average rates. Published on 31 March and 31 December each year: the spot rate at midday on that day, and the average of the monthly rates for the preceding twelve months.
• Bank of England daily spot rates. A daily statistical series of spot rates against sterling, published by the Bank each business day.

The point for choosing an API: a market mid-rate and an official table are different products. A market rate is right for showing a customer a price. It is not the figure a tax form or an auditor asks for.

The eight providers

1. AllRatesToday

Best for: teams that need both kinds of rate. Mid-market rates for 160+ currencies refresh every 60 seconds on every plan, on any base currency, over HTTPS. The same key serves the official tables of 123 central banks and 6 tax authorities, each with the publisher's own date. For the UK that means: HMRC monthly rates and Bank of England daily rates. Output is JSON, CSV, XML or Excel from the same endpoints, with SDKs for JavaScript, Python, PHP, Go and Rust and an MCP server for AI agents. Paid plans start at €4.99 a month; dated tables and history are on paid plans.

2. Frankfurter

Best for: projects that only need official fixings and want them free. Frankfurter is open source, needs no key and has no monthly cap. It now aggregates 111 central banks and official sources. For the UK its source list covers: HMRC and Bank of England. It serves official fixings, not a live market rate, and it is a free service with no paid tier or support contract.

3. ExchangeRate-API

Best for: dashboards and reports that need volume and can live with one update a day. The free plan gives 1,500 requests a month with daily updates; the Pro plan is $10 a month for 30,000 requests with hourly updates. Rates are a blended market figure, not a named institution's table.

4. Open Exchange Rates

Best for: teams that want a long-established vendor and work from a US dollar base. The free plan gives 1,000 requests a month with hourly updates on a USD base; other base currencies start with the $12 a month plan.

5. CurrencyAPI

Best for: small private projects. The free plan gives 300 requests a month with daily updates and is for private use only; paid plans start at $12.99 a month.

6. Fixer

Best for: teams already on the apilayer marketplace. The free plan gives 100 calls a month with hourly updates for non-commercial use, and base-currency switching is listed only on paid plans, which start at $14.99 a month.

7. currencylayer

Best for: the same apilayer stack with a dollar source. The free plan gives 100 calls a month with daily updates for non-commercial use; paid plans start at $14.99 a month.

8. XE Currency Data

Best for: banks and large companies that need a recognised vendor on an annual contract. There is a trial but no free plan; the entry plan is $599 a year for 10,000 requests a month with daily rates.

Try it for GBP

# live mid-market rate
curl "https://allratestoday.com/api/v1/rates?source=GBP&target=EUR" \
  -H "Authorization: Bearer YOUR_API_KEY"

# HMRC monthly rates in force
curl "https://allratestoday.com/api/open/central-bank/hmrc"

# Bank of England daily rates
curl "https://allratestoday.com/api/open/central-bank/boe"

The first call needs a free API key. The official table responses carry the table's own date, so you can show which publication a figure came from.

Which one should you pick?

FAQ

What is the best exchange rate API for the UK in 2026?

For live GBP rates plus the HMRC monthly rates and Bank of England daily rates on one key, AllRatesToday. For the same official tables free and without a key, Frankfurter. For the largest free quota of daily market rates, ExchangeRate-API.

Is there an HMRC exchange rate API?

HMRC publishes its monthly rates as CSV and XML files on the trade tariff service. AllRatesToday and Frankfurter both serve the HMRC table as JSON.

Which exchange rate does HMRC accept for VAT?

VAT Notice 700 section 7.6 says you must use the UK market selling rate at the time of the supply, or you may use the period rate published by HMRC for customs purposes. Another rate needs HMRC's written agreement.

How often are HMRC exchange rates updated?

Monthly. HMRC publishes on the penultimate Thursday of each month for the following calendar month. Spot and average rates are published on 31 March and 31 December.