GST is the tax most small Singapore businesses get wrong on timing. Either they register too late — and IRAS comes looking — or they register too early without thinking through the operational implications, and end up with an extra compliance layer they didn't need.
This piece walks through the rules and the decision. Specific positions depend on your business and should be confirmed against current IRAS guidance.
The compulsory threshold
Compulsory GST registration kicks in when your business's taxable turnover exceeds S$1 million. There are two distinct tests, and you need to pass either one to trigger registration.
The retrospective test
At the end of each calendar quarter (31 March, 30 June, 30 September, 31 December), assess your taxable turnover for the past 12 months. If it exceeds S$1 million, you have a notification obligation: you must register for GST within 30 days of the end of that quarter.
The prospective test
At any point, if you can reasonably expect that your business's taxable turnover will exceed S$1 million in the next 12 months, you must register for GST within 30 days of forming that reasonable expectation. The classic trigger: signing a contract or expanding a venue in a way that obviously crosses the threshold.
Either test alone is enough to require registration. Both run continuously — you don't have to wait until the next quarter if the prospective test bites.
What counts as “taxable turnover”
Generally, your taxable turnover includes the value of taxable supplies of goods and services made in Singapore. Some specifics worth knowing:
- Both standard-rated and zero-rated supplies count toward the threshold.
- Exempt supplies (most financial services, certain residential property dealings) generally do not count.
- Sale of capital assets (e.g. disposing of a piece of equipment) generally does not count.
- Imported services in certain circumstances do count (the Overseas Vendor Registration and Reverse Charge rules).
For F&B and retail operators, the calculation is usually straightforward — revenue is your taxable turnover. For mixed businesses (e.g. property with rental, or financial services), getting the calculation right is more nuanced.
Voluntary registration: when it makes sense
You can register for GST voluntarily before crossing the threshold. Voluntary registration is irrevocable for at least 2 years, so the decision deserves real thought.
Voluntary registration usually makes sense when:
- You have significant input tax to claim. Pre-opening capex, equipment purchases, fit-out costs — if you've paid material GST on inputs, registering allows you to reclaim that input GST.
- You sell mainly B2B. Your customers can claim back the GST you charge them, so registration is cost-neutral to them. You get to reclaim your input GST and look more credible to enterprise customers.
- You expect to cross the threshold soon anyway. Some operators register voluntarily in the run-up rather than scrambling at the threshold.
Voluntary registration usually does not make sense when:
- You sell mainly B2C. Charging GST on consumer prices either eats into your margin (if you absorb it) or makes you 9% more expensive than unregistered competitors.
- You haven't yet built the operational discipline.GST registration adds quarterly F5 filing, careful record-keeping, and from 1 April 2026, InvoiceNow obligations. Don't take it on if the bookkeeping isn't already clean.
What happens after registration
Once registered, the recurring obligations:
- Charge GST on taxable supplies at the current standard rate.
- File GST F5 returns — typically quarterly, sometimes monthly for larger businesses. Due within one month after the period ends.
- Pay net GST (output tax collected minus input tax claimed) at the same time as filing.
- Maintain GST-relevant records for at least 5 years — tax invoices, credit notes, customs documents, supplier invoices with GST detail.
- Issue compliant tax invoices with all required elements (your GST number, customer GST number where applicable, etc.).
InvoiceNow: the 2026 obligation that lands alongside
A change worth knowing about now: from 1 April 2026, businesses that voluntarily register for GST must submit invoice data to IRAS via the InvoiceNow network. The phased rollout to all GST-registered businesses then runs through 2031.
Practically, this means: if you're considering voluntary registration in 2026, your accounting system needs to be Peppol-ready (Xero is; QuickBooks Desktop and spreadsheets are not). Build InvoiceNow readiness into your registration planning. We've written a separate operator note on what 1 April 2026 actually means for your accounting stack that covers this in detail.
The two-year voluntary lock
A point operators sometimes miss: voluntary registration is irrevocable for at least 2 years. You can't register to claim input GST on a piece of equipment and then deregister three months later.
IRAS also requires that you remain registered until at least 2 years from the date of registration before you can apply to cancel — and cancellation is at IRAS's discretion based on the circumstances.
How to decide
Three questions to work through with your accountant:
- Where is your taxable turnover today, and at the current growth rate, when will it cross S$1 million?
- Is your customer base mainly B2B (registration is roughly neutral) or B2C (registration costs you margin or pricing power)?
- Do you have material input GST to claim now, or expect to in the next 12 months (capex, fit-out, equipment)?
The answers usually point clearly to either “register now voluntarily” or “wait until you're forced to”. The middle ground is rare.
How registration changes your pricing
The most often-underestimated consequence of GST registration is the pricing decision it forces. For a B2C operator who was selling at S$10 pre-registration, three options at the moment of registration:
- Raise prices to S$10.90 (price + 9% GST), preserving margin. Customers see a price increase. For non-essential discretionary spend, this can affect demand.
- Keep prices at S$10 inclusive, absorb the GST. Margin compresses by roughly the GST rate net of input claims. For thin-margin businesses (most F&B), this is painful.
- Hybrid — raise prices partially, absorb the rest. The pragmatic middle ground.
The decision depends on demand elasticity, competitive pricing in the segment, and the share of customers who are themselves GST-registered (who can reclaim the GST and don't care about the increase). It's a conversation worth having at the moment of registration, not after the first F5 cycle.
Common questions about GST registration
What counts toward the S$1M threshold — is it gross sales or net?
Gross taxable supplies, before deductions. Discounts given to customers reduce taxable turnover; commissions paid out (e.g. to delivery platforms) typically do not. Sale of capital assets is generally excluded. Confirm specifics against current IRAS guidance for your structure.
If I'm a new company expecting to cross S$1M in year one, when do I register?
Under the prospective test, you must register within 30 days of forming the reasonable expectation that taxable turnover will exceed S$1M in the next 12 months. For a new business with that trajectory, the cleanest answer is usually to register voluntarily at incorporation so the system is set up correctly from day one. The 2-year lock applies, but a new business that expects to be over the threshold isn't going to want to deregister anyway.
What happens if I cross the threshold but don't register?
IRAS treats this as late registration and may backdate the registration date to when you should have registered. You'd then be liable for GST on sales made since that date — even if you didn't collect it from customers. Penalties and interest can apply. The fix is voluntary disclosure as soon as you realise; IRAS treats voluntary disclosure more favourably than discovered non-registration.
Can I claim back GST on costs incurred before I registered?
In limited circumstances, IRAS allows claims on pre-registration expenses — typically for goods still held at the date of registration and services received within a defined period before registration. The rules are specific. Worth getting input from your accountant at the moment of registration to capture what's claimable.
If I'm a small business serving other GST-registered businesses, should I register voluntarily?
Often yes. Your business customers can reclaim the GST you charge them, so registration is essentially neutral to them. You get to reclaim your input GST on costs and look more legitimate to enterprise customers (some procurement teams won't engage with non-registered vendors above certain thresholds). The main downside is the operational layer (F5 filing, record-keeping), which is manageable once set up.
GST timing is one of the few accounting decisions where getting it right early saves money and getting it wrong is expensive in both directions.
— The Acuitas team