You crossed the threshold. Your revenue hit SGD 1 million and you registered for GST. Congratulations — and also, you now have obligations that most people don't fully explain to you when you sign up.

"Registering for GST means SMEs have to be more accountable, cannot suka suka." That's how one Singapore forum commenter put it. Blunt. Accurate.

Here's what actually changes — and what you need to set up immediately.

The Quarterly Filing Obligation

The most important thing to understand is the GST F5 return. Every GST-registered business in Singapore must file a GST return every quarter. The quarters are:

• January to March — due by 30 April
• April to June — due by 31 July
• July to September — due by 31 October
• October to December — due by 31 January

Missing a filing deadline results in a late filing fee of SGD 200. If you're persistently late, IRAS can issue a court summons. This is not a soft deadline.

Most newly registered businesses miss their first or second filing not because they're dishonest, but because nobody put the dates in their calendar and the quarter crept up on them.

What You Actually Have to File

The F5 return requires you to report:

• Total value of standard-rated supplies — what you sold that attracted 9% GST
• Total output tax — the 9% GST you collected from customers
• Total value of taxable purchases — what you bought for your business
• Total input tax — the GST you paid on those purchases
• Net GST payable — output tax minus input tax

That last line is the number you either pay to IRAS or claim back. If you collected more GST than you paid, you send IRAS the difference. If you paid more GST than you collected — common for businesses with high supplier costs — IRAS refunds you.

The Input Tax Claim Most SMEs Miss

Here's the benefit of GST registration that gets undersold: input tax claims.

Every time you buy something for your business from a GST-registered supplier, you pay 9% GST. As a GST-registered business, you can claim that back. Professional services fees, equipment, software subscriptions, office supplies — the 9% on all of these is potentially recoverable.

Most newly registered businesses don't have a systematic way to track this. They collect their supplier invoices in a folder or an email inbox and try to compile them at quarter end. Some miss invoices entirely. Some claim input tax on personal purchases incorrectly. Both create IRAS audit risk.

What IRAS Actually Looks For

IRAS audits GST returns. They look for:

• Claimed input tax on purchases that don't qualify
• Output tax that seems low relative to your reported revenue
• GST charged on invoices that doesn't match your F5 return
• Inconsistencies between your GST returns and your income tax filing

The penalty for GST fraud is severe — up to 200% of the tax undercharged plus potential criminal prosecution. This isn't a compliance area where close enough is acceptable.

Setting Up Your GST Tracking System

Before your first quarter ends, you need:

1. A way to track every sales invoice you issue — with GST amount separately identified.

2. A way to capture every purchase invoice you receive — with supplier's GST registration number and GST amount.

3. A reminder system for filing deadlines — not a mental note. An actual calendar event or automated reminder two weeks before each quarter end.

4. A reconciliation process — before you file, your total invoiced GST should match your bank deposits plus receivables. If it doesn't, something is wrong.

Most Singapore SMEs start with a spreadsheet. This works for the first few quarters. As transaction volume grows, it becomes a quarterly panic to compile everything in time.

The Common Mistakes in the First Year

Charging GST before your effective date. Your GST registration has an effective date. Charging GST before that date means you collected tax you weren't authorised to collect — a compliance issue.

Not updating your invoice template. Your invoices must show your GST registration number, the GST rate, and the GST amount as a separate line. Invoices without this format are non-compliant.

Claiming input tax on entertainment expenses. GST on entertainment — client meals, gifts — is generally not claimable. Many newly registered businesses claim it anyway.

Missing the threshold for voluntary deregistration. If your revenue drops below SGD 1 million for two consecutive years, you may be able to deregister. Missing this means continuing to file when you don't have to.

Making It Automatic

ArcPay automatically calculates GST on every invoice you send, tracks input tax on purchases, and reminds you two weeks before every quarterly F5 deadline. Your accountant gets a clean GST report at quarter end rather than a shoebox of receipts.

If you've just registered for GST and you're not sure you have the right system in place, now is the time to fix it — before your first quarter ends, not after.

Start your free 14-day trial →

No credit card required. GST tracking set up in under 5 minutes.