GST: when you must register, and what changes when you do

Goods and Services Tax is Singapore's consumption tax, charged at 9% since 1 January 2024. A registered business charges it on its sales (output tax), claims back the GST it pays on business costs (input tax), and pays IRAS the difference every quarter. The question for most companies is not how GST works. It is when they have to start, and whether starting early is worth it.

The S$1 million test, two ways

Only taxable supplies count towards the threshold. That means standard-rated sales (charged at 9%) and zero-rated sales (exports of goods and international services). Exempt supplies, such as most financial services and the sale or lease of residential property, do not count. Nor do out-of-scope supplies, or the sale of the company's own capital assets.

1. Retrospective test. At the end of each calendar year, add up taxable supplies for that year. If the total exceeds S$1 million, you must apply within 30 days, unless you can show that the next 12 months will be below S$1 million.
2. Prospective test. At any point, if you can reasonably expect taxable supplies in the next 12 months to exceed S$1 million, you must apply within 30 days of that date. A signed contract, a purchase order or a new revenue line can all trigger it.

Companies tend to watch the first test and miss the second. The prospective test is the one that catches fast-growing businesses, because it looks forward from the day the expectation arises.

A worked example

In the second row, if the company waits until year end, it will have issued four months of invoices without GST that it now has to account for. That cost comes out of its own margin unless contracts allow it to recover the GST from clients. Check your contracts say prices are exclusive of GST.

Can you be exempt?

A business that is liable to register but makes mainly zero-rated supplies can apply for exemption from registration. IRAS generally considers it when more than 90% of taxable supplies are zero-rated and the business would usually be claiming refunds. Exporters of goods sometimes use this to avoid quarterly returns, at the cost of not recovering GST on their costs.

Should you register voluntarily?

Voluntary registration comes with conditions. You must stay registered for at least two years. IRAS expects the person handling GST to have completed its GST e-learning, and it may ask for a banker's guarantee where it sees risk. And from 2026, InvoiceNow applies from day one.

InvoiceNow, the new step

InvoiceNow is Singapore's e-invoicing network, built on the international Peppol standard. Under the GST InvoiceNow requirement, a registered business sends invoice data to IRAS through an accredited solution, alongside the invoice itself. The rollout is phased:

• From 1 May 2025: any GST-registered business may adopt it voluntarily.
• From 1 November 2025: newly incorporated companies that register voluntarily must use it.
• From 1 April 2026: all new voluntary registrants must use it, whenever they were incorporated.
• Other GST-registered businesses: IRAS plans to extend the requirement in stages after further consultation. No dates have been set.

In practice this means choosing accounting software that is InvoiceNow-ready and registering a Peppol ID before you apply, not after.

What changes when you register

• Charge 9% on standard-rated supplies from the effective date of registration, and issue tax invoices with the required details
• Show GST-inclusive prices to consumers in all price displays and quotes
• Claim input tax only with valid tax invoices and only for business purposes. Some costs are blocked whatever the purpose: club subscriptions, medical expenses that are not legally required, and the costs of running private cars
• File the GST F5 return every quarter, one month after the quarter ends, and pay by the same date. Late filing brings a S$200 penalty for each month late, up to S$10,000
• Keep records for five years
• Review imported services: a registered business that cannot claim all its input tax may have to account for GST on services bought from overseas under the reverse charge

Mistakes we see most

• Counting the wrong revenue. Including exempt interest income, or leaving out zero-rated exports, gives the wrong answer to the threshold test.
• Missing the prospective trigger because the contract was signed by the sales team and nobody told finance.
• Pricing contracts "inclusive" without meaning to. If a contract is silent, the price may be treated as including GST.
• Claiming input tax on the director's car or on staff medical insurance that is not compulsory.
• Registering voluntarily for a one-off refund, then finding the two-year minimum and quarterly returns cost more than the refund.

If you are close to the threshold, the GST registration check runs both tests on your figures.