This is in contrast to other financial markets, where interest rate payments are made at daily intervals with the shortest increment of one business day. This document describes how interest rates are charged and paid.
Interest rates vary from currency to currency, and they change on a daily basis.
Hence, interest on the account balance is paid at 4pm EST each day, with an appropriate entry in the transaction table of each account. Since the account balance is held in USD, the USD borrowing rate is applied. Calculating interest on open trades is more involved. Note that in this case the customer is collecting significantly more money than they are paying, due solely to the discrepancy in interest rates between the base and the quote currencies. Note again that the borrowing rate is quoted first, followed by the lending rate, and that interest rates are quoted in percentage points per year.