If your business revenue is approaching S$1 million, GST registration in Singapore is no longer optional – it’s a legal requirement. This guide covers who must register, who should consider voluntary registration, how the application works, and what your obligations are once you’re registered.
GST registration Singapore: when it becomes mandatory
You must register for GST in Singapore if your taxable turnover in the past 12 months exceeded S$1 million (retrospective basis), or if you have reasonable grounds to expect it to exceed S$1 million in the next 12 months (prospective basis). The threshold applies on a rolling 12-month basis – not just the calendar year. Once crossed, you have 30 days to register. Failure to register on time gives IRAS grounds to back-assess GST from the date you became liable. They’ve done this.
Should you register voluntarily?
Voluntary GST registration makes sense when your clients are mainly GST-registered businesses. The GST you charge them is input tax they can claim back – so it doesn’t increase their cost. You, on the other hand, can claim back GST on your own business expenses. Net result: you get a tax refund on your costs without making your services more expensive to clients.
The maths works differently if your clients are mainly individuals or non-GST registered businesses – they can’t claim back the GST, so adding 9% either costs you the margin or costs you clients.
New from 1 April 2026: Businesses applying for voluntary GST registration must comply with InvoiceNow (PEPPOL e-invoicing). Factor this into your accounting system setup before applying.
The GST registration process
GST registration is done online through IRAS myTax Portal. You’ll need Singpass, or a tax agent can file on your behalf.
What you need before applying: your company’s UEN, financial year end date, estimated annual taxable turnover, SSIC code, bank account details for GST refunds, and (for voluntary registration) evidence of intent to make taxable supplies.
Processing time: Most straightforward applications take 10 working days. Your GST registration number arrives by post and electronically.
Your obligations once registered
Charging GST: From the effective registration date, you must charge 9% GST on all standard-rated taxable supplies. Invoices must show the GST amount separately and include your GST registration number.
Filing GST returns: Most businesses file quarterly. Form F5 is due within one month of each accounting period end. You report output tax (GST charged to customers), input tax (GST paid on business expenses), and the net amount payable to IRAS.
Keeping records: GST records must be kept for at least 5 years – tax invoices, import documents, and records supporting input tax claims.
What you can (and can’t) claim as input tax
You can claim input tax on office rent, professional fees, business travel, equipment, and staff training. You cannot claim on private car expenses, club memberships, most medical expenses, or family benefits. Mixed-use items require apportionment.
Deregistration
If taxable turnover falls below S$1 million and you don’t expect to exceed it, you can apply to deregister. IRAS requires repayment of any input tax claimed on assets you retain at deregistration (if the input tax exceeds S$5,000).
For a full overview of Singapore corporate tax obligations, see our corporate tax Singapore guide.
Get it right from the start
Wrong rates, missed filings, and incorrect input tax claims all create compliance risk. Getting proper advice at the registration stage is considerably cheaper than fixing problems after the fact. Abacus handles GST registration and filing for Singapore companies. Get in touch to discuss whether you should register and what the process involves.
