How Does IRAS Select GST Returns for Audit?
According to the Inland Revenue Authority of Singapore (IRAS), the authority completed over 2,800 GST audits in FY2024/25, recovering about S$205 million — and most GST filing mistakes Singapore businesses make are avoidable. IRAS does not select businesses for review at random: its risk-scoring system is built on filing patterns, industry benchmarks and behavioural indicators. Every Goods and Services Tax (GST) Form F5 submission therefore becomes a data point. Each sits alongside the wider compliance deadlines Singapore startups must track.
One misclassified supply or unsupported claim can push a business into the audit queue, where penalties reach twice the undercharged tax. This infographic sets out the six errors most likely to trigger IRAS queries in 2026. It also details the controls that keep quarterly returns clean.
Why Are Blocked Input Tax Expenses Still Being Claimed?
Penalties of up to 200% of the tax undercharged apply when input tax is claimed on expenses that Section 19(4) of the GST Act blocks. The provision disallows claims on motor cars, medical expenses and club subscriptions. Family benefits and private or domestic expenses are equally disallowed. Despite the law being long settled, motor car and medical claims keep slipping through. They remain among the most common errors IRAS finds on review. Screening purchase categories before each submission is essential.
When Do Exports Lose Their 0% GST Zero-Rating?
Exports lose their 0% GST zero-rating when the required export permits, shipping documents or proof of export are not maintained. IRAS allows 60 days from the time of supply to put these records in place. For goods exported from Singapore, IRAS requires commercial evidence such as:
- The export permit
- The supplier's invoice
- Transport documents like a bill of lading or air waybill showing the goods left Singapore
Where the evidence is incomplete or not retained, the supply is treated as a standard-rated local supply. Output tax at 9% must then be accounted for. GST-registered businesses should also keep payment evidence and customer details to substantiate the export.
Why Are Input Tax Claims Rejected Without Valid Invoices?
Input tax claims are rejected when the supply exceeds S$1,000 and is not supported by a full tax invoice. That invoice must contain the supplier's GST registration number. Receipts, quotations and proforma invoices do not qualify, and claims lodged before a valid tax invoice is issued are rejected on review. The same applies to invoices not made out to the registered entity. A systematic invoice verification process protects input tax refunds and keeps the GST return clean.
Why Must GST Returns Match Your Financial Statements?
Net GST errors of S$3,000 or less can be adjusted in the next return, provided the non-GST error stays within 5% of Box 4 declared supplies for the affected period. IRAS nevertheless compares each GST F5 return against the business's financial statements and general ledger, so every variance must be explained. Before each submission, match F5 Boxes 1 to 5 to the general ledger. Check Box 1 standard-rated supplies, Box 2 zero-rated supplies and Box 3 deemed supplies against the ledger's output accounts. Investigate every variance before filing rather than after IRAS raises a query. Larger mismatches require a GST F7 correction, with time limits of five years. Running the reconciliation inside a paperless compliance system keeps each quarter's figures aligned before filing.
Six GST Filing Mistakes: Rules, Thresholds and IRAS Consequences
| Filing Mistake | Rule or Threshold | Consequence |
|---|---|---|
| Claiming blocked input tax | Section 26 blocks motor cars, medical expenses and club subscriptions | Recovery with penalties of up to 200% of tax undercharged |
| Misclassifying zero-rated services | 0% GST requires export permits and shipping evidence | Zero-rating disallowed; GST recovered at the prevailing rate |
| Omitting deemed supplies | Gifts over S$200, fringe benefits and asset disposals | Output tax understated; closer inspection |
| Claiming without valid invoices | Full tax invoice needed where supply value exceeds S$1,000 | Claims rejected on review |
| Mismatching returns and accounts | Errors over 5% of declared supplies | GST F7 correction required, with time limits of five years |
| Failing to account for reverse charge | 9% self-accounting on imported services | Penalties plus interest on the shortfall |
When Must You Account for Reverse Charge on Imported Services?
Singapore's GST rate stands at 9% in 2026, making reverse charge errors costly on imported services. Reverse charge chiefly affects GST-registered businesses that are not entitled to full input tax recovery. These are typically businesses making exempt supplies that import taxable services from overseas suppliers. It does not extend to imported goods, which attract import GST at the point of entry instead. Services used entirely to make exempt supplies do not permit recovery of the self-accounted tax.
Low-value goods sold into Singapore sit under a different regime entirely. The Overseas Vendor Registration regime applies only to overseas vendors whose global turnover and Singapore low-value goods sales exceed the prescribed registration thresholds, and those vendors charge 9% GST on their Singapore sales directly rather than through reverse charge. Understated liabilities in either regime surface during compliance checks and attract penalties and IRAS late-payment penalties on the shortfall.
What Are the Rising Costs of GST Non-Compliance?
Late filing of a GST return costs S$200 per month, capped at S$10,000 per outstanding return. Beyond late-filing fees, GST non-compliance costs rise through penalties and late-payment penalties. IRAS penalties can reach 200% of the tax undercharged. Late payment attracts a one-time 5% penalty on the unpaid tax, and where the tax remains unpaid 60 days after that penalty, a further 2% is imposed for each completed month of default. Because filing errors are now surfaced through data analytics, unresolved mistakes often compound into multi-year liabilities. Professional GST administration is the most cost-effective way to contain this exposure.
How Quickly Can the Costs of GST Non-Compliance Escalate?
Within 60 days: once unpaid GST remains outstanding 60 days after the initial 5% late-payment penalty, IRAS adds a further 2% for every completed month of default, so costs escalate monthly and compound from there. Prevention costs far less than remediation once late fees, penalties and compounded shortfalls are tallied. Accurate records, pre-filing reconciliation and professional GST administration keep every quarterly return clean. That support forms part of the post-incorporation services Singapore companies rely on.
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Frequently Asked Questions
A late submission penalty of S$200 is imposed immediately, continuing monthly up to S$10,000 per outstanding return. A 5% late payment penalty also applies to unpaid tax.
Yes, provided the net GST error is S$3,000 or less and the non-GST error is within 5% of Box 4 supplies for each affected period. Otherwise, a GST F7 must be filed.
Yes. IRAS requires a nil GST return for every accounting period, even where there were no business transactions.
The return must be e-Filed within one month after the end of each accounting period through the IRAS myTax Portal, with payment due on the same date.
Tax invoices, receipts and supporting records must be retained for at least five years to substantiate the figures declared in each GST return.
Abigail Yu
Author
Abigail Yu oversees executive leadership at 3E Accounting Group, leading operations, IT solutions, public relations, and digital marketing to drive business success. She holds an honors degree in Communication and New Media from the National University of Singapore and is highly skilled in crisis management, financial communication, and corporate communications.
