Selfwealth does not pay interest on international cash balances held in your account. This applies to all international currencies, including USD and HKD.
Your international cash is held in a trust account with Citibank, managed by Selfwealth's trading partner Phillip Capital. This is a non-interest-bearing account — however, there are no fees for holding funds there either.
Want to know more about how your international cash and holdings are held?
See: How are my international holdings and cash held?