# BTO queue numbers & the 40% drop-off rate explained

Published 5 November 2026. By [Cheng Xu](https://btoradar.com/about), BTO Radar.

Getting a BTO queue number larger than the number of flats offered — such as queue number **145 out of 100 flats** (145% of supply) — does not automatically mean you missed out. Because a substantial fraction of invited applicants decline to book a flat, HDB issues queue numbers up to **300% of the flat supply** and invites applicants subject to availability and ethnic quota ([HDB booking rules](https://www.hdb.gov.sg/-/media/hdb-pulse/news/2023/hdb-launches-6800-flats-in-october-2023-bto-exercise/Annex-B-Admin-details-Oct-2023.pdf)).

## Why roughly 40% of invited BTO applicants do not book

HDB has publicly reported that around **40% of applicants invited to book a flat eventually decline to do so** ([HDB, March 2023](https://www.hdb.gov.sg/hdb-pulse/news/2023/keeping-public-housing-accessible-for-singaporeans)). This historical figure predates the October 2023 non-selection changes and is not a current forecast. Possible reasons for declining include:

1. **Remaining units do not fit the buyer's budget or floor preference**: Low-floor units, units near bin centres or substations, or higher-priced stacks may be all that remain when later queue numbers are called.
2. **HFE letter or financing gaps**: Buyers discover at the selection appointment that their HDB Flat Eligibility (HFE) loan amount or EHG grant is smaller than expected.
3. **Change of plans**: Some households buy a resale flat during the waiting period between balloting and flat selection.

## How far past 100% can a queue number still book a flat?

If a project has **U** units and an average decline rate of **d** among invited applicants, then inviting **Q** applicants yields approximately **Q × (1 − d)** bookings. For all **U** units to be taken, the queue reaches approximately **Q = U ÷ (1 − d)**:

| Share of invited applicants who decline (d) | Expected queue cutoff as % of flat supply | Example: 400-unit 4-room pool reaches queue number | Invitation probability at rate 3.0 (equal weights) |
|---|---|---|---|
| **0% (nobody declines)** | **100%** of supply | #400 | 33.3% ([reproduce](https://btoradar.com/tools/ballot-chance?rate=3&chances=2&decline=0)) |
| **20% decline** | **125%** of supply | #500 | 41.7% ([reproduce](https://btoradar.com/tools/ballot-chance?rate=3&chances=2&decline=20)) |
| **30% decline** | **143%** of supply | #571 | 47.6% ([reproduce](https://btoradar.com/tools/ballot-chance?rate=3&chances=2&decline=30)) |
| **40% decline (historical illustration)** | **167%** of supply | #667 | 55.6% ([reproduce](https://btoradar.com/tools/ballot-chance?rate=3&chances=2&decline=40)) |
| **50% decline (hypothetical)** | **200%** of supply | #800 | 66.7% ([reproduce](https://btoradar.com/tools/ballot-chance?rate=3&chances=2&decline=50)) |

You can test any application rate and decline assumption directly in the [BTO ballot chance calculator](https://btoradar.com/tools/ballot-chance).

## The non-selection penalty: why fewer people drop out carelessly now

Since the **October 2023 BTO exercise**, HDB tightened the rules on declining to book a flat ([HDB October 2023 administrative details](https://www.hdb.gov.sg/-/media/hdb-pulse/news/2023/hdb-launches-6800-flats-in-october-2023-bto-exercise/Annex-B-Admin-details-Oct-2023.pdf)):

- **First non-selection**: If you are invited to book a flat and do not select one, **first-timer applicants lose their first-timer priority (and extra ballot chances) for one year** and are treated as second-timers in BTO/SBF ballots during that year.
- **Exception for very few remaining units**: HDB waives the non-selection count when there are **10 or fewer BTO flats** (or 5 or fewer SBF flats) left to choose from at your selection appointment.
- **Cancelling after booking**: If you book a flat (pay the Option Fee) and later cancel before or after signing the Agreement for Lease, you forfeit the Option Fee (or 5% of the flat price after signing) and face a **one-year wait-out period** before applying again.

## Practical checklist if your queue number is between 100% and 200%

1. **Check the Ethnic Integration Policy (EIP) quota on the HDB Flat Portal**: Even if units remain when your queue number approaches, you can only book if your household's ethnic group still has quota left in that block and project.
2. **Track the remaining unit count before your appointment**: If 10 or fewer BTO units remain when your appointment starts, you can decline without incurring the one-year first-timer priority suspension.
3. **Prepare your cash and CPF numbers before selection day**: Run the [BTO downpayment & EHG calculator](https://btoradar.com/tools/bto-downpayment) on the lowest- and highest-priced remaining units so you know immediately at the HDB Hub appointment which units fit your 30% MSR and CPF OA balance.