GST F5 is the quarterly GST return Singapore GST-registered businesses file with IRAS. The mechanics are well-defined; the filing itself takes under an hour when done from clean data; the discipline of getting clean data over the course of the quarter is the real work.

This piece walks through what GST F5 actually asks for, how to prepare for it through the quarter, the common mistakes we see, and how to make the quarterly cycle a non-event.

What GST F5 reports

The F5 return reports, for the GST accounting period:

  • Total value of standard-rated supplies (output GST charged on local sales)
  • Total value of zero-rated supplies (exports, certain international services)
  • Total value of exempt supplies (most financial services, residential properties)
  • Output tax due (GST charged on standard-rated supplies)
  • Input tax claimed (GST paid on business purchases, recoverable to the extent attributable to taxable supplies)
  • Net GST payable or refundable

For most operating SMEs, the bulk of the return is standard-rated output GST and recoverable input GST. The zero-rated and exempt portions are usually small or nil.

The filing cycle

GST-registered businesses are assigned an accounting period by IRAS — usually quarterly (March, June, September, December year-ends), sometimes monthly for larger taxpayers. The F5 must be filed within one month after the accounting period ends.

Payment of net GST due is at the same time as filing. Most businesses set up GIRO for automatic settlement on the filing deadline.

What to collect through the quarter

The work to make the F5 filing easy happens through the quarter, not at the end. Specifically:

  • Per-transaction GST coding in your accounting system. Every sale and purchase classified by tax code at entry, not at filing time.
  • Per-supplier GST defaults set up so a new transaction defaults to the correct code.
  • Tax invoices kept on file for input GST claims — IRAS may ask to see them during a review.
  • Credit notes processed timely so sales and purchases reflect actual values at quarter close.
  • Bad debt relief claimed where applicable (specific rules; talk to your accountant).

When this discipline is in place, the F5 filing is essentially running a report from your accounting system, reviewing it, and submitting. When it isn't, the quarter-end is a scramble to retroactively code transactions.

The F5 preparation routine

For a typical Singapore SME with disciplined coding through the quarter:

  1. Day 1-3 of new quarter: run GST report from accounting system, reconcile to expected output GST (POS total × GST rate, adjusted for zero-rated portion if applicable)
  2. Day 3-5: review input GST transactions for any without supporting tax invoice; either obtain the invoice or remove the claim
  3. Day 5-7: review unusual or high-value transactions for correct coding
  4. Day 7-10: prepare the F5 figures; review with whoever owns the filing
  5. Day 10-15: file via myTax Portal; set up GIRO payment if not already in place

For most SMEs, that's 2-4 hours of work spread over two weeks. Far less than a quarter-end scramble.

Common mistakes that trigger IRAS queries

  • Output GST not matching reported revenue. If your stated standard-rated supplies × 9% should equal your stated output GST, but it doesn't, IRAS will notice.
  • Input GST claimed without supporting tax invoices.A query during a GST audit can disallow claims if invoices can't be produced.
  • Claiming input GST on non-claimable categories. Specific categories are disallowed (private use, club subscriptions, certain motor vehicles); claiming them flags the return.
  • Late filing. Penalty applies, plus interest on overdue tax. Persistent late filing escalates to enforcement action.
  • Misclassified zero-rated supplies. Treating local sales as zero-rated exports without qualifying documentation can lead to back-assessment.

The InvoiceNow change from 1 April 2026

From 1 April 2026, voluntary GST registrants must transmit invoice data to IRAS via the InvoiceNow Peppol network. Phased rollout to all GST-registered businesses through 2031.

What this changes for F5 filing: most of the data IRAS needs for F5 will already be transmitted via InvoiceNow as invoices are issued. The F5 itself may eventually simplify (or be pre-populated) as IRAS builds on this data.

For now, F5 still requires manual filing. Plan the InvoiceNow readiness ahead of the deadline. We have a deeper read on this in our operator note on what 1 April 2026 actually means.

Common questions about GST F5 filing

Can I file GST F5 myself, or do I need an accountant?

You can file yourself via myTax Portal with CorpPass. Whether you should depends on transaction volume and complexity — for small, simple operations, self-filing is reasonable. For higher volumes or any complexity (zero-rated supplies, exempt supplies, partial input claims), accountant involvement reduces error risk.

What if I made an error in a previously filed F5?

IRAS allows correction via GST F7 (Disclosure of Errors). Voluntary disclosure is treated more favourably than discovered errors. Don't wait for IRAS to find it; file the correction promptly.

What if my net GST position is a refund?

Refundable F5s are perfectly normal — businesses with significant input GST relative to output (heavy capex period, mostly zero-rated supplies) often have refund positions. IRAS may take longer to process refunds and may query for supporting documentation; keep tax invoices readily available.

How much GST should I budget for as a percentage of revenue?

For typical operations, net GST payable runs roughly 4-6% of revenue (9% output minus 3-5% input GST recovery). Highly purchase-heavy operations may run lower; service operations with low input GST may run closer to 9%. Set aside cash monthly to avoid a quarter-end cash crunch when F5 payment is due.

What records do I need to keep for GST?

Tax invoices, simplified tax invoices, credit notes, customs import permits — all required to substantiate claims. Records must be kept for at least 5 years from the relevant accounting period.

What we doAcuitas runs GST F5 preparation, review, and filing as part of the standard tax compliance service for clients. See tax & compliance.

GST F5 is one of the more mechanical compliance filings a Singapore SME has. The discipline through the quarter is what makes it routine. Get the per-transaction coding right; the F5 itself takes care of itself.

— The Acuitas team