1. Assuming first-timer status without checking
"First-timer" is a defined HDB status, not simply "I've never owned a flat." Previous grant receipt, inheritance of property, or having been listed on a previous flat application can affect your status — always verify via your HFE letter rather than assuming.
2. Miscounting household income
Income ceilings are based on gross household income including all occupiers being counted, not just the buyers' income — forgetting to include a working essential occupier's income (or wrongly including someone who isn't actually part of the application) is a frequent error.
3. Underestimating the Proximity Housing Grant distance rule
Buyers often assume a flat is "close enough" to parents without measuring the actual distance against HDB's defined radius, only to find out post-application that they fall just outside the qualifying range.
4. Not accounting for grants already used
If you or your spouse received a housing grant on a previous flat, this generally affects (or disqualifies) your eligibility for certain grants on a subsequent purchase — this is easy to overlook if buying with a new spouse who has a prior flat history.
Apply for your HFE letter before you get emotionally or financially committed to a specific flat — it's the authoritative source for your actual eligibility, not general guides like this one.