GST Charged by a Non-GST-Registered Supplier: What to Do and How InvoiceNow Flags It

Short answer: If a supplier that is not registered for GST puts GST on its invoice, you cannot claim that GST as input tax. IRAS says you should ask the supplier for a refund and leave the amount out of your GST return. Check the supplier on IRAS’s GST Registered Business Search before you pay or claim.

GST charged by a non-GST-registered supplier is a small invoice line that can become a larger problem at audit. The supplier had no right to collect the tax, so your company cannot recover it from IRAS, and any input tax already claimed has to be reversed. This guide covers why the claim fails, how to check a supplier, how to fix a wrong charge, and how IRAS’s recommended InvoiceNow validation check catches these invoices.

Raffles Corporate Services works with a panel of experienced Singapore law firms who offer cost-effective and efficient legal service and advice. This article is general information only and is not legal advice.

Can you claim input tax on GST charged by a non-GST-registered supplier?

No. Input tax is only claimable on GST that was lawfully charged by a GST-registered supplier, so GST shown on an invoice from an unregistered business is not input tax you can recover.

IRAS lists the conditions for claiming input tax on its conditions for claiming input tax page. One is that local purchases are supported by a valid tax invoice. IRAS lists “supplier is not GST registered” as an example of an invalid invoice: the supplier has no GST registration number, or the number shown has expired or is not valid.

At today’s 9% rate, a S$20,000 fit-out invoice with GST wrongly added carries S$1,800 that your company paid but cannot claim. For more on what is claimable, see our guide to input tax claims under Singapore GST.

Why would a supplier charge GST when it is not registered?

Usually by mistake: registration is pending or cancelled, or an old template still carries a GST line.

IRAS states that only GST-registered businesses are allowed to charge and collect GST. A business that has applied but has not yet been registered is not GST-registered, so it should not add GST to its invoices. Common patterns are:

• A new supplier that expects to cross the S$1 million taxable turnover threshold for compulsory registration and starts adding GST before IRAS confirms its registration.
• A supplier that has deregistered (for example, after turnover fell) but keeps using the old invoice template.
• A related business, such as a director’s other company, that is not registered even though the main company is. We cover that scenario in a director’s other business issues the invoice.

The offence of unauthorised collection under section 64A of the GST Act falls on the person who collected the GST, not on you. Your exposure is the input tax claim and the cash paid out.

How do you check whether a supplier is GST-registered?

Use IRAS’s GST Registered Business Search. It is free, public and needs no login, and you can search by business name, GST registration number or Unique Entity Number (UEN).

The search shows registration status, period of registration and GST registration number. The period matters: a “Deregistered” supplier’s invoice can be valid if dated inside its old registration period, but not after it.

What should you do if a non-GST-registered supplier has charged you GST?

Stop the claim, ask the supplier for a refund of the GST, and correct any return where you have already claimed it. You do not need IRAS’s approval to ask a supplier for a corrected invoice.

1. Confirm the supplier’s status and registration period on the GST Registered Business Search for the invoice date. Save a screenshot or PDF of the result.
2. Hold the invoice out of your next GST F5 return, so the GST is not claimed in Box 7 (input tax and refunds claimed).
3. Write to the supplier, pointing out that it does not appear on IRAS’s register for the invoice date, and ask for a refund of the GST and a corrected invoice without GST.
4. If you have not paid yet, pay only the amount excluding GST once the corrected invoice arrives.
5. Check your ledger for other invoices from the same supplier; wrong charges tend to repeat.
6. If input tax was claimed in a past return, correct it. IRAS’s GST F7, “Disclosure of Errors on GST Return”, is requested electronically on myTax Portal and can be filed up to 14 days from the date of request.

If the supplier will not refund, the amount is a cost to your company, not input tax. Recovering the money from the supplier is a contract question; if the amount justifies it, speak to a lawyer about your options.

What happens if your company has already claimed the GST?

The claim should be reversed, ideally before IRAS raises a query, to keep penalties low.

Under the IRAS Voluntary Disclosure Programme, a disclosure that is accurate, complete, timely and self-initiated qualifies for reduced penalties. Within the 1-year grace period from the statutory filing deadline, no penalty is imposed; after that, the reduced GST penalty is a flat 5% of the GST undercharged. A disclosure is only timely if made before IRAS sends a query or notice of an audit or investigation.

IRAS states that around 3,000 GST-registered businesses are selected for audit every year, that incorrect input tax claims are the most common mistake found, and that on average more than S$18,000 in GST and penalties is recovered yearly from each business. Our guide on how to correct past GST errors and voluntarily disclose to IRAS walks through the F7 process, and common GST errors Singapore businesses make covers other input tax traps.

How does the InvoiceNow validation check on wrongful GST charges work?

It is an automated check, recommended by IRAS, that compares the supplier GST number on each invoice with IRAS’s register for the invoice date and raises an alert if the number is invalid or not found.

IRAS’s guide Recommended Features for the GST InvoiceNow Requirement: Validation Check on Wrongful GST Charges (version 1.0, last updated 7 March 2025) sets out the design. InvoiceNow is Singapore’s Peppol-based e-invoicing network, introduced by the Infocomm Media Development Authority (IMDA) in 2019. For any invoice where GST is more than zero, the accredited software sends the supplier’s GST number to IRAS’s Check GST Register API (application programming interface). It then checks two things:

1. The registration status returned is “Registered” or “Deregistered”; and
2. The invoice date falls within the supplier’s registration start and end dates.

If both conditions are met, the invoice data goes through; if not, the software raises an alert. IRAS recommends running the check daily at invoice level.

For a buyer, the Type 1B and Type 3 alerts flag a purchase invoice with an invalid supplier GST number before you claim the GST. Two limits apply: this is a recommended feature, so not every InvoiceNow-Ready Solution includes it, and an alert does not block a purchase submission, so someone still has to act on it.

When will your business be on InvoiceNow?

All GST-registered businesses must submit invoice data to IRAS through InvoiceNow-Ready Solutions, in phases running to 1 April 2031. Until your phase starts, check suppliers manually.

According to IRAS’s GST InvoiceNow Requirement page, the phases are:

• 1 November 2025: companies that register for GST voluntarily within 6 months of incorporation.
• 1 April 2026: businesses applying for voluntary GST registration on or after that date.
• 1 April 2028: businesses applying for compulsory registration on or after that date, and existing GST-registered businesses with total annual supplies of S$200,000 or less.
• 1 April 2029, 1 April 2030 and 1 April 2031: existing GST-registered businesses with total annual supplies of up to S$1 million, up to S$4 million, and above S$4 million respectively.

Total annual supplies means Box 4 of the GST returns for periods ending in calendar year 2025. IRAS says it has notified businesses registered before 2026 of their implementation date from mid-2026. For the practical setup, see our guide to getting an InvoiceNow Peppol ID and switching on GST submission.

How can you stop wrong GST charges reaching your GST return?

Build the supplier check into onboarding and your quarterly GST review.

• Record each supplier’s GST number and registration start date in your supplier file.
• Recheck the register when a supplier’s invoices start or stop showing GST.
• Claim input tax in the accounting period that matches the invoice date, as IRAS requires.
• Ask your InvoiceNow software provider whether the wrongful GST charge validation is switched on, and who in your team receives the alerts.

If you are a supplier unsure whether you should charge GST at all, try the GST Registration Checker on our free tools page. If you prefer to hand the GST review to someone else, our packages page lists GST Filing at S$450 for existing clients and S$550 for new clients, and a GST add-on to our quarterly bookkeeping packages from S$300 per quarter.

Frequently asked questions

Can I claim the GST if the supplier registers for GST later?

Not on an invoice dated before the registration took effect. The invoice date must fall within the supplier’s registration period.

Is my company liable for the supplier’s unauthorised GST collection?

No. The section 64A penalty for collecting GST without authority falls on the business that collected it. Your company’s risk is claiming input tax it is not entitled to, and the cash paid to the supplier.

What if the invoice shows a GST number that belongs to another company?

Treat it as invalid. Search the number on the GST Registered Business Search; if the registered name does not match your supplier, do not claim and query the supplier.

Does the InvoiceNow validation check replace manual checks?

Not entirely. Not every solution offers it, and for purchase invoices it alerts without blocking the submission, so someone still needs to follow up.

Last reviewed: 26 October 2026. The Editorial Team, Raffles Corporate Services.