Verify Supplier UEN & GST Before Paying an Invoice (Singapore)

A Singapore supplier invoice arrives with a UEN at the top, often a GST registration number beside it, and frequently a 9% GST line at the bottom. Before approving payment, the AP team has four things to confirm:

1. The UEN exists in BizFile — the entity behind the invoice is a real, registered business and the registered name matches what the invoice shows.
2. The GST registration is active as of the invoice date in IRAS's myTax Portal GST Registered Business Search — not just registered today, but registered on the supply date.
3. The registration is not de-registered or suspended at the supply date — a previously registered supplier may have lost status since you last paid them.
4. The registered principal activity is consistent with the invoice line — a registered cleaning-services supplier billing you for IT consulting is a flag worth documenting, even if it is not necessarily fraud.

The reason all four matter, and why the second is where most invoices that get paid in error come unstuck, is the effective date. Take a S$10,000 invoice dated 1 March 2026 from a supplier whose GST registration effective date in IRAS is 15 April 2026. The supplier was not a registered taxable person on the supply date. The S$900 of GST charged on that invoice is unrecoverable input tax — IRAS will not allow it on your GST F5 even though the supplier printed a registration number on the document. The right AP response is to withhold payment of the GST line, request a revised invoice without GST, and document the IRAS lookup against the supplier record.

That worked example carries through this entire piece because it is the failure mode the SERP rarely walks. Most generalist Singapore GST-check content treats the IRAS register as the single check and stops at "the supplier is registered, so claim the input tax." The four-check framing above splits the work into the questions actually being answered, and separates the two registers that answer them. BizFile (run by ACRA) is the entity-existence register. IRAS's myTax Portal GST Registered Business Search is the GST-registration register. They serve different questions, both have to clear, and conflating them is the structural error that lets effective-date mismatches slip through.

This article covers the buyer-side workflow to verify supplier UEN and GST registration before paying an invoice in Singapore. It does not re-walk the issuer-side question of 11 mandatory fields a Singapore tax invoice must carry — that is a separate piece for when you are designing your own invoices, not verifying someone else's. It also does not cover the foreign-supplier case where no Singapore GST is charged at all and the buyer accounts for tax themselves; for that, see reverse charge for imported services from foreign suppliers. What follows assumes a UEN and GST registration number are already on the invoice in front of you, and walks the four checks that turn those fields into a defensible payment decision.

---

Check 1 — UEN Exists in BizFile, and the Format Sanity-Check Before You Look

BizFile (bizfile.gov.sg) is the entity-existence register run by ACRA. A BizFile UEN search returns the registered entity name, the entity type, the registration date, and the current status — live, struck off, dissolved, in liquidation, and so on. That is what answers check 1: the UEN belongs to a real entity, the entity is currently in good standing, and the registered name lines up with what the invoice says the supplier is called.

Before you open the portal, the UEN itself often tells you whether the search will return anything. Singapore UENs come in three formats, each tied to entity type, and any AP clerk who reads enough invoices learns to spot a wrong one at a glance.

• 9-character format (nnnnnnnnX) — ACRA-registered businesses such as sole proprietorships and partnerships, and the older numbering still carried by some long-established entities. Eight digits and a check letter.
• 10-character format (yyyynnnnnX) — local companies registered before 2009, where yyyy is the year of incorporation, nnnnn is the serial number, and X is the check letter. A Pte Ltd incorporated in 2005 will look like 200512345A.
• 10-character format (TyyPQnnnnX) — every other entity issued from 2009 onward. T represents the 2000s, yy is the year, and PQ is the entity-type code: LL for an LLP, LP for a limited partnership, FC for a foreign company branch, CC for a charity, SS for a society, and so on. An LLP formed in 2018 looks like T18LL1234A.

That three-format guide turns the UEN into a first-pass red flag. A Pte Ltd whose UEN starts with T-yy-LL is not a Pte Ltd. An LLP that hands you a 9-character UEN with no entity-type code is not an LLP. Wrong character count, an entity-type code that contradicts how the supplier presents itself, or a string that does not parse to one of the three formats above is almost always a typo on the invoice and occasionally something that warrants a phone call before you spend time on the IRAS lookup.

For a new supplier going onto the master, the BizFile search is part of onboarding alongside the IRAS check. Run both, save the BizFile screenshot with the date of the lookup, and store it against the supplier record. The audit value of the check sits in being able to produce that record on demand, not in remembering you did the search once two years ago. When BizFile returns the entity, also note what it says under registered principal activity — that is the field check 4 will compare against the invoice line, and capturing it now avoids re-running the search later.

Check 2 — IRAS GST Registered Business Search and the Effective-Date Reading

The IRAS myTax Portal GST Registered Business Search is the GST-registration register. It sits at mytax.iras.gov.sg, requires no login, and accepts a lookup by UEN or by registered name. The result returns the GST registration number, the registered name, the GST registration effective date, and — when applicable — a de-registration date. Those four fields are the entire output, and they are enough to verify GST registration number against what the supplier printed on the invoice and to read the effective date against the invoice date.

The reading you need to do is mechanical, but the conclusions matter. Three combinations come up in practice:

• Effective date on or before the invoice date, no de-registration date. The supplier was a registered taxable person on the supply date. The GST line is supportable for input tax provided the rest of the invoice (the issuer-side fields, the underlying supply) holds up. This is the case AP wants to see.
• Effective date after the invoice date. The supplier was not registered on the supply date. Any GST charged on the invoice is unrecoverable input tax — IRAS will not allow it on your GST F5, regardless of what the registration number printed on the invoice shows.
• De-registration date present and on or before the invoice date. The supplier had de-registered by the supply date. Any GST charged is similarly unrecoverable, and the invoice should have been issued without GST in the first place.

The opening worked example is the canonical case for the second combination. A S$10,000 invoice dated 1 March 2026 from a supplier whose IRAS effective date is 15 April 2026 carries S$900 of GST that the AP team cannot claim. Save the IRAS screenshot, time-stamped, against the supplier record. The operational response — what to pay, what to hold, how to handle a supplier who insists the registration was active — sits in the failure-mode section further down, because the same default applies whichever of the four checks fails.

One note on the GST registration number itself. A registration number printed on the invoice is evidence the supplier claims to be registered; it is not a check. The number can be valid in format and still belong to a supplier whose registration was effective only after the invoice date, or whose de-registration date precedes the invoice. The lookup is what confirms the GST registration number against status and effective date — the field on the invoice does not.

The screenshot or PDF print of the IRAS result is the audit artefact that ties this section back to the rest of the workflow. Store it the same way as the BizFile result: against the supplier record, with the date of the lookup. The Knowledge Principle section later in this article explains why that record is the documentary backbone of an input-tax claim, not just a tidy filing habit.

Check 3 — De-Registered or Suspended Mid-Relationship

Onboarding-time verification is a snapshot. A supplier who was registered when you first paid them two years ago can de-register voluntarily — most commonly because revenue dropped below the registration threshold and the entity decided the compliance load was not worth maintaining — or have the registration cancelled by IRAS for compliance failure, MTF investigation, or dissolution of the underlying entity. When that happens, the supplier should stop charging GST on new invoices. The GST line on the invoice does not always update with reality.

The way to catch this is a quarterly batch re-check across the supplier master, scheduled around the GST F5 cycle so that the verification record is current when the return is prepared. Run the same IRAS lookup for every active supplier and watch for two things: a new de-registration date that did not exist last quarter, and any change of registration status that suggests suspension. A new de-registration triggers a hold on subsequent invoices from that UEN and a conversation with the supplier; the historical record of input-tax claims for periods when registration was active stays intact.

When a supplier de-registered GST charging shows up — the supplier is invoicing GST on the current document, but their de-registration date in IRAS falls on or before the invoice date — the AP response is straightforward. Stop accepting GST on new invoices with that UEN. Retain the existing audit evidence for prior periods (the original IRAS lookups, the supplier-issued tax invoices, the payment records — these remain valid for the windows when registration was active). Request a revised invoice without GST for the current document, and treat the relationship from this point forward as if the supplier were unregistered.

Suspension is rarer than de-registration but works the same way for AP purposes. GST charged during a suspension window is not supportable for input tax, and the invoice gets the same treatment as a de-registered one until the supplier produces evidence the suspension has been lifted.

A word on cadence. Quarterly is the floor, not the ceiling. For high-value supplier relationships or for suppliers whose status looked borderline at the last check (a recent registration, a thin-revenue entity, anything that flagged on activity-match in check 4) shorter intervals or per-invoice spot-checks are reasonable. The right cadence is the one the AP team can actually run consistently. An aspirational monthly check that gets skipped half the time produces worse audit evidence than a disciplined quarterly check that always runs — and the discipline is what the Knowledge Principle frame downstream actually rewards.

Check 4 — Does the Registered Activity Match the Invoice Line

BizFile records each entity's registered principal activity, typically as an SSIC code with a short description (62012 — Information technology consultancy services, 81211 — General cleaning services of buildings, and so on). Check 4 is the comparison: does what the invoice line items describe line up with what BizFile says the supplier does?

Mismatch is not the same as fraud, and treating it that way damages perfectly good supplier relationships. Legitimate suppliers expand into adjacent activities without updating their BizFile registration straight away, and some Pte Ltds carry a deliberately broad principal activity that genuinely covers a wide range of work — "holding companies" and "business and management consultancy" are particularly catch-all. The standard AP response is to document the mismatch on the invoice, ask the supplier in a brief email to confirm the work was actually performed, and decide whether to escalate. The mismatches that warrant escalation rather than just a confirming email are the ones where the gap is materially wide, where the invoice value is high relative to the supplier's payment history, or where the activity flag stacks on top of other smaller flags on the same supplier — a UEN that scraped through with a typo correction, a registration effective date that landed close to the invoice date, and now an activity mismatch on a S$50,000 invoice is a controls-review conversation, not an email.

The point of check 4 is not to catch every mismatch in the supplier book. It is to make sure the AP team has a documented look at the question, so that if a downstream audit ever asks why a particular invoice was accepted, the answer is not "we did not look".

---

When a Check Fails — The AP Team's Response

The default response when any of the four checks fails has the same shape: do not approve the GST line, document the failure with the supporting register screenshot and a dated note, and request a revised invoice from the supplier that reflects the actual position. The detail differs by check.

Check 1 fails — the UEN does not resolve in BizFile. Hold the entire invoice. A non-existent UEN is far more likely to be a typo on the document than a fraudulent supplier, but the supplier needs to confirm the correct UEN and re-issue. Do not work around it by guessing a similar-looking UEN that does resolve — that puts the wrong entity on your supplier record and creates a tidier-looking error than no record at all.

Checks 2 or 3 fail — the GST registration is not active at the supply date, or it is de-registered or suspended at the supply date. This is where most of the operational pain in Singapore AP actually lands, and the response is to hold the GST line specifically rather than the whole invoice. If the underlying supply is genuinely valid and the supplier confirms the GST should not have been charged, pay the net amount and ask for a revised tax invoice without GST. If the supplier insists they were registered, ask them to send their own IRAS print-out — that conversation usually resolves quickly because the supplier can either produce the print-out (in which case re-run your own lookup carefully, sometimes you searched the wrong UEN) or they cannot, in which case they had quietly known and were trying it on.

Check 4 fails — the activity does not match. Document the mismatch on the invoice, get a written confirmation from the supplier that the work was performed and how it sits within their registered activity, and decide whether to escalate. Most activity mismatches resolve at the email-confirmation stage; the small minority that do not should go to whoever owns supplier compliance review at the SMB. Do not treat this check as a payment block by default — the documented look is the control, not the blanket rejection.

The audit artefact in every case is the same shape: the BizFile screenshot, the IRAS screenshot, the dated note describing what failed and how it was resolved, the supplier correspondence, and the revised invoice where one was issued. Store these against the supplier record in whatever form the SMB's filing system actually supports — a folder per supplier on the shared drive, an attachment field in the accounting system, or a structured row in the supplier-controls spreadsheet. The form does not matter. The retrievability does.

A practical note on accounting-software integration. Xero, MYOB, and QuickBooks SG all carry supplier-record fields for UEN and GST registration number, and those fields are useful for storing the values you have verified. None of the three enforces effective-date matching at pay time. None will warn you that the supplier's GST registration effective date is later than the invoice date, because none holds the IRAS register data to compare against. The check is operational, not automatic — the workflow above is what fills the gap the accounting software does not.

---

Verifying at Scale — The 4-Entry IRAS Cap and the Quarterly Bulk Check

Single-invoice verification scales linearly with the AP team. Supplier-master verification does not, because the IRAS GST Registered Business Search supports only a small number of simultaneous entries per query — the portal currently caps the single-search form at four UENs at a time. For a supplier master in the low hundreds that is tedious; for one in the thousands it is unworkable. This is the workflow constraint that nobody who quotes "use the IRAS register" actually grapples with, and it is the reason most Singapore SMBs end up with a gap between the verification cadence they say they run and the verification cadence they actually run.

There are three realistic ways to bridge that gap.

• Quarterly batch lookups via myTax Portal. Manual, free, suitable for supplier masters in the low hundreds where the AP team has dedicated time scheduled around the GST F5 cycle. The work is repetitive but the data is authoritative and the artefact (a folder of dated screenshots) is exactly what an audit asks for.
• Commercial credit and compliance services. The Singapore-active arms of Dun & Bradstreet, Experian, and the regional APAC equivalents offer paid bulk-verification feeds that include UEN existence, entity status, and GST-registration status — usually as part of a wider supplier-data product. Worth the spend for SMBs whose master is in the thousands or whose audit posture warrants it.
• AP-automation platforms and Peppol-network connections. InvoiceNow-connected systems and several mid-tier AP platforms can validate counterparties at intake. Coverage and depth vary considerably by vendor, and the validation is not a substitute for the IRAS effective-date check on individual invoices, but it does catch the basic UEN-existence and current-registration cases automatically.

Whichever route you take, the data prerequisite is the same: a clean ledger of supplier UENs, GST registration numbers, and the invoice dates and totals they have appeared on. AP teams that maintain that ledger as a structured artefact — even a spreadsheet, updated as invoices arrive — can run a quarterly verification cycle in an afternoon. AP teams that do not end up reconstructing it from a folder of PDFs every cycle, which is where the cadence quietly slips.

Converting the supplier-invoice corpus into that ledger up front is what makes the bulk verification viable in the first place. Pulling supplier UEN, GST registration number, vendor legal name, invoice date, GST amount, and total out of a heterogeneous bundle of supplier PDFs into a single structured spreadsheet is exactly what our AI invoice data extraction for Singapore AP teams is built to do — describe the fields you need, upload the batch, and download an Excel, CSV, or JSON file that feeds straight into the IRAS lookup or a commercial verification feed. The product is the upstream extraction step, not the verification tool itself; the verification is yours to run against IRAS and BizFile.

For AP teams whose remit covers more than Singapore, the same control runs in adjacent jurisdictions with different registers and different failure modes — the Australian ABN verification workflow for the same AP control is the closest structural sibling and worth reviewing if your shared-service centre processes both.

---

The Knowledge Principle — Why the Four Checks Are Audit Defence, Not Hygiene

Since 1 January 2021, IRAS has applied the Knowledge Principle: input tax is denied, with a 10% surcharge on top, for any supply the buyer knew or should have known formed part of a Missing Trader Fraud arrangement. The phrase that does the work is "should have known." It converts supplier verification from a hygiene practice the AP team chooses to run into the regulatory baseline IRAS expects to see when input-tax claims are challenged. The absence of UEN and GST-register checks is itself evidence the buyer did not exercise the reasonable diligence the standard requires — and that absence shows up clearly in audit, because there is nothing to produce.

The regulatory anchor sits in the input-tax conditions IRAS itself publishes. The IRAS conditions for claiming input tax list, as conditions for claiming input tax, that the goods or services must be supplied by a GST-registered supplier and that the claimant must hold a valid tax invoice issued by that supplier. Read the four checks in this article against those two conditions and they line up directly. Check 1 establishes the supplier is who they claim to be — the entity whose name appears on the tax invoice actually exists. Checks 2 and 3 confirm the supplier was a GST-registered taxable person at the supply date, which is the condition's bite (registration status today is irrelevant if it was not active on the date of supply). Check 4 supports the genuine-supply test by tying the invoice line to a registered activity the supplier could plausibly have performed.

That re-frames the audit artefact built up over the previous sections. The BizFile screenshots, the IRAS screenshots, the dated notes describing what was checked and what was found, the supplier correspondence, the revised invoices retained where the original was wrong — these are the documentary record an IRAS audit asks for when input-tax claims are challenged. The same artefacts also feed the GST F5 evidence trail. A tidy verification record at intake means a clean reconciliation at quarter end; the verification work and the reconciliation work draw on the same documents. (For the quarter-end side of that, see the companion piece on reconciling Box 5 and Box 7 on the GST F5 from supplier invoices.)

UEN and GST verification is the baseline layer of MTF defence, not the whole of it. The deeper layer — chains of related entities, payment patterns that do not match the underlying supply, missing-supply indicators where the goods or services on the invoice do not appear to have been delivered — sits beyond the four checks here. The Singapore Missing Trader Fraud AP due-diligence checklist covers that layer in the detail it warrants. Run both layers and the "should have known" standard becomes a control you can demonstrate, not a question you have to answer in retrospect.

What the four-check workflow actually delivers is a documented control. The AP team can produce it on request. The SMB's external accountant can audit against it. The input-tax claims on the GST F5 carry a defensible foundation rather than a printed registration number and a hope that nobody asks.