HMRC monthly exchange rates
HMRC publish one exchange rate per currency per calendar month. This calculator converts every foreign trade with them, and every month it holds has a page here.
Divide, do not multiply
An HMRC rate is the number of units of a foreign currency you get for one pound. Sterling is therefore the foreign amount divided by the rate. Multiplying instead is wrong by the square of the rate, and it is the most common mistake made with this table.
HMRC do not prescribe which exchange rate you use. CG78310 expects a reasonable and consistent method, and the monthly rate is the method this calculator applies to every trade. What CG78310 does settle is the date: sterling worth is taken at the date of the acquisition or disposal (Bentley v Pike, Capcount Trading v Evans). A broker's own rate and a market feed are neither published nor consistent, so this site never reads one.
Where these rates come from
Two HMRC sources, because the older months are not on the newer service.
- January 2021 onwards. The Online Trade Tariff publishes a CSV per month. This is the file behind October 2026: https://www.trade-tariff.service.gov.uk/api/v2/exchange_rates/files/monthly_csv_2026-10.csv
- Before January 2021. The Trade Tariff answers 404 for those months, so they come from HMRC's own XML archive, which is what the gov.uk collection links to for monthly rates up to December 2020. This is the file behind December 2020: http://www.hmrc.gov.uk/softwaredevelopers/rates/exrates-monthly-1220.XML
Both are listed in the gov.uk collection Exchange rates for customs and VAT. A rate comes from HMRC or it does not come at all.
Months held here
2018 8 months
2019 11 months
2020 12 months
2021 12 months
2022 12 months
2023 12 months
2024 12 months
2025 12 months
2026 10 months
What a rate is for
- A trade in a foreign currency is converted at the rate for the month it was made, on both legs. A buy in one month and a sale in another use two different rates, and that is the point of a dated table.
- A gain is computed in sterling, not converted after the event. CG78310 puts the sterling worth at the date of the acquisition or disposal.
- Excess reportable income from an offshore fund converts the same way, at the month the income arises. The ERI lookup shows which month it used.
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