HDB to condo: the honest arithmetic of upgrading in Singapore

Upgrading is sold as a lifestyle decision and executed as a financing decision. The part that goes wrong is almost never the choice of project. It is the arithmetic underneath it, and it goes wrong in four specific places.

1. Your sale proceeds are smaller than you think

When you sell an HDB flat, the money does not all arrive as cash. In order: the outstanding housing loan is redeemed, the CPF principal you originally withdrew is refunded to your Ordinary Account, and the accrued interest on that principal — 2.5% a year, compounded, for every year you have owned the flat — is refunded alongside it. What is left after selling costs is your cash proceeds.

The accrued interest is the number people miss. On $250,000 of CPF used fifteen years ago, the accrued interest alone is well over $110,000. It is not lost — it goes back into your CPF Ordinary Account and you can use it again for the next property — but it is not cash, and it cannot pay a stamp duty bill.

2. The TDSR ceiling usually binds before the LTV limit

Everyone knows the loan-to-value limit is 75% for a first housing loan. Fewer people realise that the Total Debt Servicing Ratio usually caps the loan lower than that, and it is the lower of the two that decides what you can buy.

TDSR limits your total monthly debt obligations to 55% of gross monthly income. Crucially, the bank does not test that against the rate you are being offered. It stress-tests at a medium-term rate floor of 4% per annum, even if your actual package is 2.6%. Variable income — commission, bonus, allowances — is discounted by at least 30% before it counts, and rental income needs a stamped tenancy with at least six months to run.

Two constraints also apply to tenure: the maximum is 35 years for private property, and the loan-to-value limit drops by 20 percentage points if the tenure runs past 30 years or past your 65th birthday. A long tenure that improves your TDSR can quietly destroy your LTV.

3. Buying before selling triggers ABSD — and a strict clock

If you buy the condominium before you have sold the flat, you own two residential properties on the day of purchase. A Singapore Citizen pays 20% Additional Buyer’s Stamp Duty on the second property. On a $1.8M purchase that is $360,000, payable within 14 days of the sale and purchase agreement, in cash.

A married couple including at least one Singapore Citizen can claim that back in full, but only if every condition is met. The second property must be bought in both names only. Neither spouse may have owned an interest in more than one residential property each at the date of purchase. The first property must be sold within six months of the purchase date of the second — or within six months of the TOP or CSC date if the second property was uncompleted at purchase, whichever is earlier. The refund must be applied for within six months of that sale.

Since 2 July 2023 the refund is automatic for e-stamping submissions where you declared the intention to sell and claimed the refund in the form — it lands within about six weeks of stamping the sale of the first property. If you did not declare it, you are on the manual path.

4. Sequencing: sell first or buy first

For a new launch bought under the Normal Payment Scheme, buying first is often the better structure, because progressive payments spread the drawdown over years and the six-month ABSD clock runs from TOP rather than from purchase. For a resale condominium with a 12-week completion, selling first is usually cleaner.

The rules that changed recently

• Seller’s Stamp Duty was tightened on 4 July 2025: a four-year holding period at 16% / 12% / 8% / 4%. This applies to your onward purchase too, not just the flat you are leaving.
• The HDB concessionary loan LTV was lowered from 80% to 75% on 20 August 2024.
• The 15-month wait-out period for private property owners buying a resale flat was removed on 28 July 2026 — relevant if you ever want to reverse this move.
• Executive Condominiums on land tendered from 8 May 2026 carry a 10-year Minimum Occupation Period rather than five. If an EC is on your list, check the tender date of the site.