HPIS stand for Home Protection Insurance Scheme and is a mortgage-reducing insurance scheme which helps the insured members and their families pay off their outstanding housing loans in the event of the insured members' permanent incapacity or premature death before age 65.

Members who are using CPF to pay their monthly housing loan installments on their HDB/HUDC flat under the Public Housing Scheme (PHS) have to be insured under HPIS, provided they are in good health at the time they apply for cover. Members who are not using CPF to pay their monthly housing loan repayment may choose not to be insured. However it is not recommended as housing loan is usually the largest liability a person has.

You can read more on HPIS on the following CPF weblink:
CPF Board - Ask Us - Explore FAQ