A resale flat can be viewed in fifteen minutes.
The financial decision may last twenty-five years.
HDB’s resale Option to Purchase, or OTP, creates a controlled bridge between those two timescales.
Once buyer and seller agree on a resale price, the seller may grant the buyer the HDB-prescribed OTP. That document gives the buyer a defined 21-calendar-day option period in which to confirm financing, obtain the HDB value where required and decide whether to convert the negotiated deal into a binding purchase.
For the whole resale path, read How an HDB Resale Transaction Works. For the whole housing system, return to How HDB Works in Singapore.
This article reflects HDB guidance available on 4 September 2026.
Quick Answer
HDB requires resale buyers and sellers to use the prescribed OTP. The current mechanism is:
AGREE PRICE → SELLER GRANTS OTP → BUYER PAYS OPTION FEE → 21-DAY OPTION PERIOD → REQUEST FOR VALUE / FINANCING CONFIRMATION → BUYER EXERCISES OTP OR LETS IT EXPIRE
HDB currently states:
- Option Fee: mutually agreed between buyer and seller, from $1 to $1,000;
- Option Period: 21 calendar days, including weekends and public holidays;
- Option Exercise Fee: negotiated, but together with the Option Fee the total deposit cannot exceed $5,000.
Official HDB guidance: Option to Purchase When Buying a Resale Flat.
Wait, What? The OTP Is Not the Same Thing as Buying the Flat
When the seller grants the OTP, the buyer has not yet exercised it.
The buyer has obtained a temporary exclusive right to buy the flat at the agreed price under the prescribed terms.
During this period, the seller cannot grant another OTP to a different buyer.
The state is:
PRICE AGREED, OPPORTUNITY RESERVED, FINAL BUYER COMMITMENT NOT YET MADE.
The OTP Freezes One Side of the Market Temporarily
Before the OTP, the seller can continue negotiating with the market.
After granting the OTP, HDB states that the seller cannot grant another OTP until the existing one expires.
That gives the buyer something valuable:
time without losing the flat to another buyer.
The Option Fee is the price of that temporary exclusivity.
The Option Fee Is Small but Structurally Important
The Option Fee is negotiated between buyer and seller within HDB’s current $1-to-$1,000 range.
It forms part of the eventual resale price if the buyer proceeds.
If the buyer allows the OTP to expire, the Option Fee is forfeited.
This makes the initial commitment non-zero without forcing the buyer to make the entire purchase immediately.
Why 21 Days?
The option period creates a decision window.
The buyer may need to:
- confirm the financing route;
- submit the Request for Value;
- wait for the value outcome;
- confirm a bank Letter of Offer where applicable;
- review the flat and transaction again;
- decide whether the required cash remains acceptable.
The point is not to create suspense.
It is to prevent a large housing decision from collapsing into the pressure of one viewing appointment.
The Request for Value Happens Inside This Window
If the buyer will use CPF savings and/or a housing loan, HDB requires a Request for Value after the seller grants the OTP.
HDB currently requires the request by the next working day after the Option Date.
The buyer must wait for the value outcome before exercising the OTP when CPF or a housing loan is involved.
This creates a carefully ordered path:
AGREE PRICE FIRST → OBTAIN OPTION → REQUEST VALUE → SEE FINANCING CONSEQUENCE → DECIDE WHETHER TO EXERCISE
The next article owns the valuation mechanism.
The Buyer Cannot Simply Request the HDB Value Before Negotiating
Under the current resale process, the HDB value is obtained after the seller has granted the OTP at an agreed price.
This means the buyer must negotiate without knowing the final HDB value for that transaction.
Past transaction data can help estimate the likely market range.
But estimation is not the same as the official value used for CPF and financing.
This Is Why COV Risk Exists
Suppose the buyer agrees to $700,000.
The HDB value later comes back at $680,000.
The $20,000 difference is Cash Over Valuation.
CPF Board states that COV cannot be paid with CPF savings and must be paid in cash; housing loans are also based on the relevant value or purchase-price limits rather than financing the amount above valuation.
The OTP period therefore protects the buyer by creating time to discover whether the negotiated price produces a cash gap before exercising.
Exercising the OTP Is the Bigger State Change
If the buyer decides to proceed, all buyers sign the Acceptance portion of the OTP and return it to the seller within the Option Period.
The buyer also pays the Option Exercise Fee.
HDB states that the Option Fee and Option Exercise Fee together form the deposit and cannot exceed $5,000.
Now the state becomes:
OPTIONAL RIGHT → EXERCISED CONTRACT.
This is much more serious than simply having the seller’s promise held open.
If the Buyer Does Not Proceed
The buyer can allow the OTP to expire.
HDB states that the Option Fee is then forfeited and the buyer does not continue to the resale-application stage.
The seller regains the ability to transact with another buyer after expiry.
The flat returns to the market.
Bank Financing Adds a Letter-of-Offer Gate
If the buyer is taking a housing loan from a financial institution, HDB requires a valid Letter of Offer before the OTP is exercised.
This prevents the buyer from making the binding commitment on the assumption that bank financing will somehow appear later.
The loan state has to be sufficiently real before the purchase state moves forward.
HDB Loan Buyers Need the Right HFE State Before OTP Is Granted
For a buyer intending to use an HDB housing loan, HDB requires a valid HFE letter indicating HDB-loan eligibility before the seller grants the OTP.
This is another example of sequencing.
The public lender’s eligibility decision comes before the private resale contract.
The HDB-Prescribed Form Matters
Buyer and seller must use the HDB-prescribed OTP.
HDB’s current terms state that other or supplementary agreements relating to the sale or purchase are not valid under the Housing and Development Act.
The price declared to HDB must be the true resale price.
This protects the integrity of the transaction and the data used by the housing system.
The Seller Has a State Gate Too
A seller must register an Intent to Sell before granting an OTP.
HDB currently requires a seven-day cooling-off period after the Intent to Sell is registered before the OTP can be granted.
Official seller guidance: Option to Purchase When Selling a Flat.
The transaction therefore has preparatory states on both sides.
After Exercise, Buyer and Seller Must Move in Coordination
The OTP includes an agreed number of days for submission of the resale application.
HDB currently requires buyer and seller to submit their respective portions within that agreed period and within seven days of each other.
The private contract now hands the transaction into HDB’s approval machinery.
Failure Mode: Paying a Large Option Fee to Show Seriousness
The maximum Option Fee is set by HDB.
More money is not needed to make the buyer emotionally more committed.
The purpose is to enter the prescribed contract correctly, not to perform seriousness through side payments.
Failure Mode: Exercising Before the Buyer Understands COV
HDB requires the flat value to be available first where CPF or a housing loan is being used.
Use that control.
A buyer who discovers a large cash gap should understand it before turning the option into a binding purchase.
Failure Mode: Treating 21 Days as 21 Days to Negotiate Again
The price has already been agreed when the seller grants the OTP.
The option period is primarily a due-diligence and financing window for the buyer, not an invitation to repeatedly reopen the agreed terms.
Forward Play: Follow the Option
The seller grants it.
The flat is temporarily unavailable to competing buyers.
The buyer checks financing and value.
Then one of two things happens.
EXERCISE → CONTRACT CONTINUES
or
EXPIRE → OPTION FEE LOST, FLAT RETURNS TO MARKET.
Reverse Play: Start From a Successful Resale Application
For the resale application to exist, the OTP had to be exercised.
For the OTP to be safely exercised, the buyer had to know the financing state and, where required, the HDB value.
For the buyer to obtain the OTP, the seller had to grant it after the price was agreed.
The 21-day contract window is therefore the hinge connecting negotiation to formal transfer.
The Deepest Answer
The HDB resale OTP exists because buyer and seller need a state between conversation and commitment.
Too early, and the buyer may not know whether CPF, valuation and financing fit.
Too late, and the seller cannot reasonably hold the flat indefinitely.
The Option Fee buys a bounded period of exclusivity.
The 21 days create time for the hidden financial structure to become visible.
Exercise converts the possibility into a contract.
It is a small document doing a very large coordination job.
Continue Through the HDB System
Return to How HDB Works in Singapore.
Previous: How an HDB Resale Transaction Works.
Next: How HDB Resale Valuation Works | Why the Agreed Price and the Financing Value Can Be Different.