The Interest Rate for margin orders is charged 3 times per day:

at 12:00 am UTC,

at 8:00 am UTC, and

at 4:00 pm UTC.

The interest is always charged in the quote currency. For example, for the BTC/USDT pair, the interest is charged in USDT for both shorts and longs.

The interest is only charged for the positions that are open at the time of the charge. For example, if the position is closed at 7:59 am UTC, no interest will be charged at 8:00 am. If the position is opened at 7:59 am, the interest will be charged at 8:00 am.