International expenses/purchases

> You can buy goods and services in the currency of your choice. But all purchases or sales must be converted into sterling for VAT purposes.

https://www.gov.uk/guidance/foreign-currency-transactions-vat-and-tour-operators

You can either use market rates at the time (which isn't too much hassle if you're looking up rates for 2 receipts on 2 different days, but looking up 30 days of exchange rates is a _problem_) or the [HMRC's exchange rates](https://www.gov.uk/government/publications/hmrc-exchange-rates-for-2015-monthly) (these seem to work out a little better if there's lots of fluctuation as well).

Start by reading the issue's GOV.UK guidance and HMRC exchange-rate links. Determine what guidance the FAQ should provide for converting international purchases and sales to sterling, then confirm the finished documentation explains a practical approach for multiple receipts and cites the relevant HMRC source.

Written by the indexing model from the issue text.