Who owes a resale levy
The resale levy applies to households who received a housing subsidy on a previous flat (e.g. a BTO or subsidised resale purchase) and are now buying a second subsidised flat directly from HDB (BTO/SBF) or with certain CPF grants. It does not apply if your next purchase is an unsubsidised resale flat without applicable grants, in most cases.
How much is owed
The levy amount depends on the flat type of your previous subsidised flat and household size at the time (singles typically owe a reduced amount relative to families). It's a fixed quantum set by flat type, not a percentage of your sale price.
The resale levy is deducted from your sale proceeds at completion of your CURRENT flat's sale, or payable in cash if proceeds are insufficient — factor it into your net proceeds calculation before planning your next purchase budget.
Why this trips people up
Some sellers assume the levy only applies to a second BTO purchase, but it can also apply when using certain CPF grants on your next resale flat if your previous flat was subsidised. Check your specific situation via HDB before finalising your next purchase plans.