Set a rate currency on a project or a time entry. New entries use the project currency when set, or the default invoice currency for the context. Changing a project currency does not change saved entries. The invoice editor shows unbilled time in the invoice currency. Older entries without a currency can be updated in Time Tracking before invoicing. CSV exports now include the rate currency.
Rate currencies for tracked time
Time entries now record the currency of an hourly rate, and invoices offer entries that match their currency.