Sale of Balance Flats, comprising unsold leftover flats from past BTO launches, surplus flats from SERS projects, old repurchased flats (including flats from some divorced or fiance couples), are done “when HDB accumulate sufficient flats“, usually twice per year, but this is NOT A RULE. Since 2010 the SBF exercise is done same day with a BTO launch.

In May 2015 HDB announced that have 9,000 unsold flats that will be offered in two SBF exercises concurrent with May and August BTO launches, but in press release of 1 July 2015 HDB announced that the exercise was delayed to September, then the BTO launch was cancelled and mixed up with November BTO launch, and SBF was done at same time. Reason: HDB needed extra time to implement the new schemes of 2-Room Flexi and grants.

Fiance-fiancee couples who break up and do not get married within 6 months after receiving keys, as well as other people who for whatever reason need to sell the flat back to HDB during minimum occupation period, need to pay a penalty of 5% of market value of the flat, but more severely, they lose the first-timer status, and the flat is sold again via Sale of Balance Flats.