Interest is calculated by IBKR daily on a per currency basis, and is reflected on client statements in an accrued state. It is important to note that interest is calculated on settled funds, therefore, if you close a negative cash balance through a trade on Monday, interest will continue to accrue on the negative balance until the trade settles.
Clients should also note that short stock collateral and futures risk margin are backed out when determining the principal amount subject to interest, which could bring a positive cash amount into negative territory, thereby accruing interest.
More information on how interest is calculated can be found on our website.
Accruals will remain in the account until the beginning of the following month, at which point the accrual is reversed and posted as a cash item.