It is important to note that changing your Base Currency does not convert existing cash balances or change the denomination of a security into any other currency.
The particular currency used to purchase and settle any given instrument, or meet the cash variation on a futures product, is determined by the listing exchange, rather than the broker. Accordingly, if you enter into a transaction to purchase a security which is denominated in a currency that you do not hold and, assuming that you have sufficient margin excess, IBKR will create a loan for those funds. Note that this is necessary as we are obligated to settle that trade with the counterparty (i.e., clearinghouse) solely in the designated currency of denomination.
If you do not wish to have such a loan created and incur its associated interest costs, you would need to either first deposit funds into your account in the required denomination and amount or convert existing funds in your account using either our FXCONV (for amounts under USD 25,000 or equivalent) or IdealPro (for amounts in excess of USD 25,000 or equivalent) venues, both available through the TWS. If performing a conversion and you maintain a Cash type account, that conversion trade will need to settle before the funds are available to apply to any subsequent transaction.
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