Do I need to pay back HDB grants

Do take note that when you sell your house, you’ll need to refund the grant amount plus accrued interest (of 2.5% per year) back to your own CPF account. This is on top of any CPF savings used to pay for your house.
The first $60,000 of the housing grants will be credited back to your CPF OA account, while the remaining grant amount will be put into your CPF Special Account / Retirement Account and Medisave Account.