ADDITIONAL BUYER STAMP DUTY (ABSD)
It is a tax payable when you purchase or acquire a residential property i.e. applicable to both HDB flats and Private Properties.
The rate that you need to pay depends on your nationality (and/or your PR status).
It is to be paid by buyer within 14 days after the date of documents (e.g. Sale & Purchase Agreement) if the document is signed in Singapore.
If the document is signed overseas, it has to be paid within 30 days after date of its receipt in Singapore. Stamp Duty is to be paid to IRAS (Inland Revenue Authority of Singapore).