The Built-to-Order or BTO system was implemented after a review of the method of selling flats in 2001.

Prior to this, HDB sold flats under the Registration of Flats System (RFS). Every buyer in the queue was promised a flat, resulting in a waiting time of 7 years at its peak.

However, the 150,000 households in the queue did not reflect real demand. The queue disappeared when the Asian Financial Crisis hit, and HDB was left with 20,000 unsold flats.

Today, HDB will build new flats under the BTO system only when a good majority of flats in a project are booked. The BTO system allows HDB to build according to real demand and to respond flexibly to the needs of flat buyers.

It also provides greater certainty to flat buyers. Majority of first-time applicants have a chance to select a BTO flat within two tries. Flat buyers can look forward to possession of their flats 3 years after booking.

The BTO system allows HDB to ramp up new flat supply quickly when demand is high. Conversely, when demand is low, HDB will scale back to avoid oversupply.