Singapore Goods and Services Tax (GST) registration generally becomes compulsory when taxable turnover exceeds S$1 million under either of two tests. The retrospective test looks at a calendar year. The prospective test looks at a supported forecast for the next 12 months. Their application deadlines and effective dates differ. First identify the test and the evidence behind it. Do not charge GST before the effective date confirmed by IRAS.
Calculate taxable turnover before looking at revenue alone
The threshold concerns taxable turnover, not every item of accounting revenue. IRAS defines this around taxable supplies made in Singapore in the course of business. Check the entity, supplies and locations being assessed.
Reconcile the turnover figure to accounts and invoices. Identify zero-rated, exempt and out-of-scope items for tax review, especially where the business operates overseas. This guide does not determine the GST treatment of an individual supply.
- Entity and GST registration unit being assessed.
- Singapore taxable supplies by month and category.
- Zero-rated, exempt or out-of-scope items requiring review.
- Reconciliation to accounts and source invoices.
Apply the retrospective calendar-year test
At the end of the calendar year, check taxable turnover from 1 January to 31 December. If it exceeded S$1 million, the usual application window is 1 to 30 January of the following year. Registration usually takes effect on 1 March of that year.
This is not a rolling 12-month test. Document the calculation and check any exception before the deadline. IRAS describes an exception for some businesses with evidence of lower future turnover that are not liable under the prospective test. Do not assume it applies without checking the conditions.
- Calendar-year taxable turnover total.
- 1 to 30 January application window if the test is met.
- Expected 1 March effective date under the usual retrospective timetable.
- Evidence for any claimed exception.
Monitor the prospective 12-month test when facts change
The prospective test applies when the business can reasonably expect taxable turnover above S$1 million in the next 12 months. Apply within 30 days of the forecast date. For liabilities arising on or after 1 July 2025, registration takes effect two months from that date.
Keep evidence such as signed contracts, accepted orders or fixed-fee invoices. A sales target alone may not support the forecast. Record when the expectation became reasonably supportable: that date determines the application deadline and expected effective date.
- Forecast date and decision record.
- Signed contracts, accepted orders or recurring invoices.
- 12-month taxable-turnover model.
- 30-day application deadline and expected effective date.
Separate compulsory and voluntary registration
A business below the compulsory threshold may consider voluntary registration. This brings ongoing duties as well as possible input-tax recovery. Check the applicable minimum registration commitments and conditions before deciding.
Model the effect on prices, cash flow, invoices and return preparation. IRAS requires specified people for many voluntary applications to complete its GST e-learning course and quiz unless exempt. Obtain advice for the actual supply chain and application type.
- Reason for registering and customer-price impact.
- Input-tax assumptions and supporting invoices.
- Accounting, invoicing and return-filing readiness.
- E-learning, GIRO and continuing-obligation checks.
Prepare the application pack and authority to file
Prepare the documents required for the business constitution and registration type before opening myTax Portal. Connect the turnover calculation or forecast to accounts, contracts, orders and invoices. Keep the applicant's legal identity clear.
Confirm who may file and who will answer IRAS questions. Save the application, attachments, acknowledgement and correspondence. Overseas entities, imports, joint ventures or unusual supplies may need specialist review.
- Business registration and authorised-person details.
- Turnover calculation and supporting transaction evidence.
- Bank, accounting and supply-chain information requested by IRAS.
- Submission copy, acknowledgement and query owner.
Plan for the effective date before approval arrives
An approval notice gives the GST registration number and effective date. Start charging and collecting GST on taxable supplies from that date, not before it. A late compulsory registration can be backdated.
Prepare invoice templates, prices, accounting codes and communications in advance. Check transactions that span the effective date. Assign record keeping, input-tax evidence and return preparation to named owners, and retain the IRAS notice.
- Confirmed GST number and effective date.
- Invoice, receipt and credit-note changes.
- Contract and customer communication plan.
- Accounting, record-keeping and return calendar.
Sources and discussion
- IRAS — Do I need to register for GST (official)
- IRAS — Applying for GST registration (official)
- IRAS — Responsibilities of a GST-registered business (official)
Related resources
Prepare the next step
Use JurisLane's company setup document checklist to organise the entity, contracts, accounts and operating facts, then confirm the GST calculation and application with IRAS or a qualified Singapore tax adviser.
Editorial note: This guide supports issue preparation and qualified review. Applicable requirements depend on the facts, entities, markets and current law.