7 Common GST Filing Mistakes Singapore SMEs Make

GST filing mistakes in Singapore are more common than most SMEs realise — and IRAS does not need to audit you before penalties apply. The most frequent errors include wrong input tax claims, misclassified exempt supplies, missed zero-rated transactions, and late submissions. This checklist helps you catch these errors before you hit submit, not after a letter arrives. 

If you handle GST filing in Singapore for your company, you already know the pressure. Quarterly deadlines, a stack of invoices, supplier queries — and the constant worry that something slipped through. IRAS collected over S$13.5 billion in GST revenue in FY2022/23, and compliance enforcement has only tightened since the rate increase to 9% in January 2024. The stakes are real. 

Run through this checklist before every submission. It is designed for in-house bookkeepers who want to file with confidence, not discover a problem six months later. 

Mistake 1: Claiming Input Tax on Disallowed Expenses 

This is one of the most common GST filing mistakes in Singapore. Not every business expense qualifies for input tax credit. IRAS specifically disallows claims on medical expenses for staff, club memberships, and motor car costs — even if these were legitimate business purchases with valid tax invoices. 

Checklist question: Before you submit, ask yourself — have you checked every input tax claim against the disallowed list in the GST Act? 

• Medical and dental expenses (unless required by law)

• Family benefits and personal insurance for employees

• Motor car expenses (S-plated vehicles)

• Club subscription fees and entertainment costs with private elements 

Claiming any of these in error can trigger an IRAS audit. Remove them from your input tax column before submission. 

Mistake 2: Misreporting Zero-Rated vs. Exempt Supplies 

Zero-rated supplies (like exports) are taxable at 0% — you can still claim input tax on related expenses.

The supplies of most financial services and residential property rentals are exempt supplies and you will not normally be able to claim input tax on costs associated with them.

It's a common mistake to confuse one with the other, which can lead to over-claiming back taxes, or under-claiming output tax. Both results will leave you in IRAS' bad books.

Checklist answer: Yes, I have correctly classified all the revenue lines as standard-rated, zero-rated or exempt before filing.

Mistake 3: Not considering imported services

A new regime for GST accounting of imported services under reverse charge applies to GST-registered businesses in Singapore from 1st January 2020. This encompasses payments to vendors outside of Bangladesh for digital services, consultancy, software license and cloud platforms.

This is something that many SME bookkeepers miss, particularly when it comes to recurring SaaS or foreign freelancer payments which appear as a regular running expense. 

Checklist question: Have you reviewed all overseas vendor payments made this quarter and applied reverse charge where required? 

Mistake 4: Using Invoices That Do Not Meet Tax Invoice Requirements 

A valid input tax claim must be supported by a tax invoice that meets IRAS requirements. The invoice must show the supplier's GST registration number, the GST amount charged, and a clear description of goods or services. 

Simplified tax invoices are allowed for amounts below S$1,000. For anything above that threshold, a full tax invoice is mandatory. Claiming input tax on an incomplete or informal receipt is an error that frequently surfaces during IRAS reviews. 

Checklist question: For every input tax claim above S$1,000, do you have a valid full tax invoice on file? 

Mistake 5: Late or Missed GST Submission 

GST returns must be submitted within one month after the end of each accounting period. Miss that deadline and IRAS will issue a late submission penalty of S$200 per month, up to a maximum of S$10,000. A 5% late payment penalty applies on any tax outstanding as well. 

Many SMEs file on time but underpay. Both scenarios attract penalties. 

Checklist question: Is your submission date calendared at least one week before the IRAS deadline to allow for internal review?

Infraction	IRAS Penalty
Late GST return submission	S$200/month, up to S$10,000
Late payment of GST	5% of outstanding tax
Incorrect return (negligence)	Up to 200% of tax undercharged

Mistake 6: Not Adjusting for Credit Notes and Bad Debt Relief 

If you issued a credit note after previously charging GST, that adjustment must be reflected in the return for the period the credit note was issued. Many bookkeepers forget to reduce their output tax accordingly. 

Equally, if a customer has not paid their invoice within 12 months and the debt is written off, you may be eligible to claim bad debt relief — effectively recovering the GST you already paid to IRAS. This is an often-missed entitlement. 

Checklist question: Have you cross-checked your accounts receivable ageing report for overdue debts older than 12 months that qualify for bad debt relief? 

Mistake 7: Incorrectly Handling the GST Rate Change Impact 

Since 1 January 2024, the GST rate in Singapore is 9%. However, transitional rules apply to contracts and invoices that straddled the rate change — particularly for supplies that were partially invoiced or paid before the rate shifted. 

Some SMEs are still applying 8% to invoices that should carry 9%, or vice versa, especially on long-term service contracts. IRAS published specific transitional guidance, and errors here tend to compound over multiple quarters before anyone notices. 

Checklist question: Are all invoices dated from 1 January 2024 onwards — and any transitional invoices from the 2023/2024 change — using the correct rate? 

Your Pre-Submission Self-Audit Checklist 

Before you file each quarter, run through these seven checkpoints: 

• Removed all disallowed input tax claims (medical, car, club)

• Correctly classified zero-rated vs. exempt supplies

• Applied reverse charge on imported services from overseas vendors

• Verified all input tax claims above S$1,000 have valid full tax invoices

• Submission date confirmed and calendared before the IRAS deadline

• Credit notes and bad debt relief adjustments processed

• GST rate of 9% applied correctly to all relevant invoices

 If any item triggers a "not sure," resolve it before you submit. IRAS's myTax Portal provides official GST e-filing guidance and the current GST Act provisions at iras.gov.sg — it should be your first reference when a classification is unclear. 

Getting these seven areas right consistently is what separates SMEs that file cleanly from those that face follow-up queries, amended returns, and penalty letters. If your team needs a second set of eyes or wants to outsource the review entirely, WZ WU & Co. offers dedicated GST services for Singapore SMEs — covering compliance reviews, GST registration, and ongoing filing support.

Frequently Asked Questions 

What happens if I make a GST filing mistake in Singapore?

IRAS may issue a penalty of up to 200% of the tax undercharged, depending on whether the error was due to negligence or intent. Voluntary disclosure before IRAS detects an error typically results in reduced penalties — so correcting mistakes quickly matters. 

How do I correct a GST error after submission in Singapore?

For errors below S$1,500 (net GST), you can adjust in the next return. For larger errors, you must submit a voluntary disclosure via IRAS's myTax Portal. Early disclosure reduces penalties significantly and demonstrates good faith compliance. 

What is the deadline for GST filing in Singapore?

GST returns must be submitted within one month after the end of your accounting period — typically quarterly. For example, if your quarter ends 31 March, your filing deadline is 30 April. IRAS accepts e-filing via myTax Portal only. 

Can I claim GST on all business expenses in Singapore?

No. IRAS disallows input tax claims on certain expenses even when a valid tax invoice exists. Common disallowed items include staff medical costs, private car expenses, and club memberships. Always verify against the GST Act before claiming. 

What is reverse charge and which Singapore businesses does it affect?

Reverse charge requires GST-registered businesses to self-account for GST on imported services from overseas suppliers. It applies when those services would be taxable if bought locally. It commonly affects SMEs using overseas software, digital platforms, or consultancy services.

Is bad debt relief automatic under Singapore GST rules?

No. You must actively claim bad debt relief in your GST return. Conditions include writing off the debt in your accounts, the debt being outstanding for over 12 months, and having originally accounted for output tax on that supply.