As clients trading global products are likely to hold positions which are denominated in various currencies, a single currency needs to be chosen for the purposes of translating statement balances. In designating this single, or Base Currency, many clients elect the currency of their country of residence or where the majority of their income and assets are denominated.

Margin Compliance: margin compliance is decided by comparing Equity With Loan Value and the margin requirement of the account.  

As cash or securities denominated in one currency may serve as collateral to satisfy the margin requirement of a position denominated in another, a common currency is required to decide whether the account is margin compliant.

Fees: charges related to market data and research, inactivity fees, exposure fees and commission on Forex trades are also charged in the designated Base Currency.

This is intended to minimize currency conversions that would otherwise be required to satisfy these fees.