A SORA-linked home loan can look simple: take a published benchmark, add the bank’s spread, and you have the interest rate. In practice, borrowers also need to understand what period the benchmark measures, when their package resets and what happens after any promotional or lock-in period.
This guide explains those moving parts without trying to predict where rates will go. SORA can rise or fall, and the cheapest package today need not remain the cheapest over a home loan’s long tenure. The useful comparison is therefore not just today’s headline rate, but the contract, fees and effect of less favourable scenarios.
What SORA measures
The Singapore Overnight Rate Average, or SORA, is administered by the Monetary Authority of Singapore (MAS). MAS defines it as the volume-weighted average rate of eligible unsecured overnight borrowing transactions in the Singapore-dollar interbank cash market between 8am and 6.15pm. It is based on actual transactions and is published on the next business day.
That overnight rate is not usually the number a homeowner sees in a mortgage formula. A housing loan may instead reference a compounded SORA tenor, commonly three months. The official MAS SORA benchmark page is the appropriate place to check the benchmark and methodology rather than relying on a rate quoted in an old article or advertisement.
How three-month compounded SORA works
Three-month compounded SORA reflects daily overnight SORA readings accumulated over a historical three-month period. Compounding recognises that interest accrues on interest through that period. It is backward-looking: it describes overnight funding conditions that have already occurred, not a forecast for the next three months.
This distinction matters. A single day’s SORA can move without immediately producing the same-sized change in the three-month compounded figure, because the latter contains roughly three months of observations. As older observations roll out and newer ones enter, the compounded benchmark changes progressively. Smoothing does not make the rate fixed; it only means changes in daily SORA feed through over time.
Borrowers should also distinguish the benchmark tenor from the loan’s reset schedule. “Three-month compounded SORA” identifies the reference rate, while the letter of offer states when that reference rate is observed and how often the mortgage rate and instalment are reset. Do not infer the exact reset date from the product name.
The all-in rate is SORA plus the bank’s spread
A package described as “three-month compounded SORA plus 0.80%” has two components. The SORA component varies with the published benchmark; the 0.80% spread is the bank’s contractual margin for the stated period. If the applicable compounded SORA were 1.20%, the illustrative all-in nominal rate would be 2.00%. This example explains the formula only and is not a current quote.
The spread may not stay unchanged for the entire loan. Some packages use a promotional spread before moving to a higher “thereafter” spread. Other terms can matter as much as a small rate difference: lock-in length, prepayment penalties, sale-within-lock-in treatment, repricing fees, legal-subsidy clawbacks and whether the package bundles another product.
Before accepting an offer, request the residential property loan fact sheet and letter of offer. Check the benchmark tenor, observation date, reset frequency, spread in every period and the effective interest rate. MoneySense’s official guide to how home loans work says the fact sheet should set out the repayment schedule, lock-in, penalties and an illustration of rate changes.
Reset timing can delay the effect on your instalment
A falling published benchmark does not necessarily reduce next month’s payment. Your current rate may have been fixed at the previous reset, and the contract may use the benchmark observed on a specified date. The new all-in rate takes effect only according to that schedule. The same lag applies when the benchmark rises.
Ask the lender for four dates or rules in writing: the benchmark observation date, the interest-rate reset date, when a revised instalment is notified and when it is first collected. Also ask whether the bank changes the monthly instalment, the allocation between principal and interest, or both. These details prevent a common budgeting error: multiplying today’s published SORA by an outstanding balance and expecting that result to match the next debit.
When repricing or refinancing deserves a review
Repricing means moving to another package with the same bank; refinancing means moving the loan to another lender. Either can reduce future interest, but the gross rate saving is not the same as the net benefit. Compare costs over the period you realistically expect to keep the new package, not over an assumed full loan tenure.
- Confirm the current lock-in end date and any early-redemption penalty.
- Check legal, valuation, conversion and administrative fees, plus clawback of subsidies.
- Compare the new promotional and thereafter rates on the same outstanding balance and remaining tenure.
- Model unchanged, lower and higher benchmark scenarios rather than relying on one forecast.
- Consider whether an intended sale, partial prepayment or change in income could occur during the new lock-in.
For an HDB flat, there is an additional one-way feature: a borrower who moves from an HDB concessionary loan to bank financing cannot later refinance that bank loan back to HDB for the same flat. Our guide to HDB versus bank loan trade-offs explains this and the wider differences in repayment flexibility. Borrowers using CPF may also want to review the implications of keeping a CPF OA mortgage buffer.
Why a lower SORA does not remove TDSR constraints
The Total Debt Servicing Ratio compares all monthly debt obligations with gross monthly income. Under current MAS requirements, a financial institution must calculate the property loan under application using the higher of a 4% residential medium-term interest-rate floor or the package’s thereafter rate. If that thereafter rate is SORA-linked, MAS says the lender uses the latest relevant SORA plus the spread. Where TDSR exceeds 55%, the loan amount has to be reduced.
The official MAS TDSR calculation guide also makes clear that financial institutions may adopt more conservative practices. Consequently, a lower payable mortgage rate can improve actual monthly cash flow without increasing the maximum loan available under the stress test. Existing car loans, credit facilities and other debts can also affect the calculation.
TDSR is a regulatory ceiling, not a recommended household budget. Loan approval, refinancing eligibility and the final quantum still depend on the applicable rules and the lender’s assessment. A prudent review leaves room for income disruption, maintenance, insurance, taxes and a future rate reset.
A contract-first checklist for SORA borrowers
Start with the current official benchmark, then read the package rather than guessing at rates. Record the all-in formula for each loan period, reset mechanics, lock-in, fees and prepayment terms. Compare offers using the same balance and tenure, and test payments at rates above the initial offer. Keep enough cash or CPF liquidity for disruptions, subject to the relevant CPF rules.
SORA-linked financing offers transparency because the benchmark is publicly administered, but transparency is not certainty. The spread, reset timing and contractual costs determine how the benchmark reaches your household budget. This article is general educational information, not personalised financial advice; obtain current written terms and assess them against your own circumstances before committing.
