Singapore Missing Trader Fraud: AP Due Diligence Checklist

Missing Trader Fraud in Singapore is not only a problem for the missing supplier. From 1 Jan 2021, IRAS can deny input tax on purchases a GST-registered business knew or should have known were part of a Missing Trader Fraud arrangement, and may impose a 10% surcharge on the denied input tax, according to IRAS guidance on Missing Trader Fraud and the Knowledge Principle. For an AP team, that turns a supplier invoice into more than a payment document. It becomes evidence for whether the buyer took reasonable, risk-based steps before approving the transaction and supporting an input-tax claim.

A Singapore missing trader fraud AP due diligence checklist should therefore answer three questions before payment moves. Does the supplier look like a real counterparty for this type of trade? Does the invoice packet support an actual supply, with documents that make commercial sense together? If something looks unusual, did the buyer pause, ask the right questions, escalate, and keep the evidence?

MTF is a fraudulent supply-chain arrangement. A supplier may charge GST, issue invoices, collect payment, and then disappear without accounting for the output tax. The buyer's exposure arises when IRAS concludes the buyer knew or should have known the purchase was connected to the arrangement. The risk is different from ordinary invoice error. It is also different from a payment-diversion scam where the buyer is tricked into sending money to the wrong bank account. MTF asks whether the underlying transaction, supplier, goods movement, and GST claim were commercially credible.

The Knowledge Principle is practical rather than academic for AP. It does not require an AP clerk to prove tax fraud. It does require the business to show that warning signs were taken seriously. A valid-looking invoice from a GST-registered supplier is useful, but it is not the full answer if the supplier was newly formed, the goods description is vague, the delivery evidence is thin, the margin is commercially odd, or the payment request points somewhere inconsistent with the supplier file.

The defensible operating model has three parts. First, supplier onboarding creates a baseline for legal identity, GST status, business activity, and contact details. Second, each higher-risk invoice is checked against that baseline and against the purchase, delivery, and payment evidence. Third, the buyer keeps a dated decision record: what was checked, what looked unusual, what evidence resolved it, who approved the conclusion, and whether the transaction was held or escalated.

Supplier onboarding KYC sets the baseline before the first invoice

Supplier onboarding is where the buyer forms its first view of whether the counterparty is plausible. The point is not to turn AP into an investigation unit. It is to create a record that says the supplier's legal identity, GST status, business activity, people, contact details, and trading profile were checked before the first GST-bearing invoice entered the payment run.

Start with legal identity. Capture the supplier's UEN, legal name, entity status, and registered address from BizFile or the ACRA business profile. Compare that profile with the trade being proposed. A newly incorporated supplier registered for a broad or unrelated activity should not automatically fail review, but it should not be treated the same as an established supplier whose registered activity, website, references, and order history all match the goods or services being bought.

GST registration needs the same discipline. Check whether the supplier is GST-registered, record the effective date, and keep the evidence with the supplier master record. A valid GST registration is necessary before the supplier can charge GST, but it is not enough by itself. A GST registration effective date very close to the first high-value invoice is a risk signal when combined with weak trading history, unusual pricing, or vague delivery evidence.

A practical Singapore supplier due diligence checklist for GST should also cover the people and commercial footprint behind the entity:

• the named directors or authorised representatives the buyer dealt with;
• a verifiable business phone number and email domain, not only a mobile number or free email account;
• website, office, warehouse, or operating address checks where relevant to the transaction size;
• trade references or prior transaction history for higher-value suppliers;
• public-record or adverse-media searches for unusual concerns;
• a risk grade that determines whether ordinary approval is enough or finance leadership needs to review the supplier.

Keep the evidence, not just the result. The onboarding file should show the source checked, the date checked, the person who checked it, the document saved, and any exception note. If a controller later asks why a supplier was approved, "UEN checked" is too thin. "ACRA profile downloaded on 12 Feb 2026, GST registration checked, business activity matched electronics distribution, trade reference obtained, finance manager approved high-risk supplier file" is reviewable.

Supplier master changes should reopen the file. A change in legal name, GST status, bank account, registered activity, address, or contact person is not routine data maintenance when MTF risk is in scope. It is a reason to refresh the baseline before the next invoice is approved.

Invoice-level red flags AP should check before approval

The invoice review is where onboarding evidence meets the transaction in front of AP. A supplier may have passed basic KYC months earlier, but each invoice still needs to make commercial sense against the purchase order, goods received note, delivery note, payment instruction, and the supplier's known business.

Begin with identity and GST basics. The supplier legal name, UEN, GST registration number where shown, address, and bank details should align with the approved supplier master. The invoice should also meet the ordinary Singapore tax-invoice rules before input tax is claimed. For that layer, use a separate field-level review against Singapore GST tax invoice requirements, then continue the MTF review instead of stopping there.

The MTF question is whether the documents support an actual supply. AP should look for consistency across the invoice packet:

• the PO describes the same goods or services as the invoice;
• the GRN or delivery note supports quantity, delivery date, and receiving location;
• the goods description is specific enough to identify what was bought;
• pricing, GST amount, and margin do not look commercially artificial for the goods involved;
• delivery route and logistics evidence match the transaction value and goods type;
• the payment account belongs to the supplier or has an approved, documented explanation.

Singapore fictitious invoice supplier red flags usually become visible as combinations, not isolated quirks. A new supplier issuing a high-value invoice for vague electronics goods is one concern. The same supplier asking for urgent payment to a third-party or offshore account, with no clear delivery evidence and a representative who cannot be verified, is a much stronger reason to stop the transaction.

Other AP-level red flags include pre-arranged trades where the buyer is told exactly who to buy from and sell to, fixed margins that do not reflect commercial negotiation, goods that appear to move on paper but not physically, invoices with round-number values unsupported by line detail, and suppliers whose registered activity does not fit the goods billed. Refusal to provide ordinary documents is itself evidence. A legitimate supplier may be busy; it should still be able to explain what it sold, where it came from, who delivered it, and why the payment instruction is valid.

The review should end with a conclusion, not only a checked list. "No mismatch identified" is acceptable for a low-risk transaction. For a higher-risk invoice, the file should say what was unusual, what evidence resolved it, and who accepted the residual risk. If the documents do not show a real supplier, real goods or services, and a real delivery path, the invoice should not keep moving merely because the payment date is close.

The audit-defence file should show the checks, evidence, and conclusion

An audit-defence file is useful only if it lets someone reconstruct the buyer's decision. A folder full of invoices and screenshots may prove that documents existed, but it does not prove that the buyer assessed them. The file should connect the risk, the check, the evidence, and the conclusion.

For a GST-bearing supplier invoice with MTF risk, keep the record at transaction level. The supplier onboarding file shows who the supplier is and why it was approved. The invoice file shows why this specific transaction was accepted, held, or escalated. Together, the record should cover:

• supplier onboarding evidence, including UEN, ACRA or BizFile profile, GST registration status, effective date, business activity, and approval;
• the tax invoice, PO, GRN, delivery note, contract or order confirmation, correspondence, and payment confirmation;
• bank-account verification or approved exception notes where payment instructions changed or looked unusual;
• a red-flag assessment that names any issue found and the evidence used to resolve it;
• the approver, approval date, escalation outcome, and any decision to hold or reject the transaction.

The record should distinguish clean, resolved, and escalated cases. For a routine supplier invoice, "no issue found after supplier and invoice checks" may be enough if the underlying checks are visible. For a higher-risk invoice, write the conclusion in a way a later reviewer can follow. If the supplier's business activity looked mismatched, what document explained the mismatch? If the GST registration date was recent, what other evidence supported the supplier's trading substance? If the delivery route was unusual, who confirmed it and where is that confirmation saved?

This is also where document extraction can help without pretending to decide tax risk. Finance teams can extract supplier invoice data for AP review by converting invoices, POs, GRNs, delivery notes, and payment confirmations into structured Excel, CSV, or JSON data. Invoice Data Extraction can capture fields such as vendor name, invoice number, invoice date, totals, GST amount, PO references, line items, and source-file or page references, giving reviewers a cleaner dataset to compare against the underlying documents. The tool does not determine whether a supplier is fraudulent and does not replace the judgment or tax advice behind the conclusion.

Keep the evidence with the transaction and GST input-tax support so it is retrievable by invoice number, supplier, reporting period, and approval date. The same supplier-invoice dataset feeds the period-end working papers when the team builds Box 5 and Box 7 of the GST F5 return from supplier invoices, so MTF-related holds, exclusions, or disallowed input tax should be visible in that reconciliation rather than handled only as an AP-side note. The file should not depend on one AP staff member remembering why a payment went through. If the buyer later needs to explain its position, the record should show the checks performed at the time, not a reconstruction prepared after the audit letter arrived.

High-risk sectors deserve tighter controls, especially prescribed goods chains

MTF risk is not evenly distributed across every purchase. Ordinary recurring suppliers still need basic controls, but AP should apply a higher review level where the goods, supplier profile, or transaction structure resembles known MTF patterns. Singapore enforcement history and IRAS guidance point especially to fast-moving, high-value supply chains where goods can be traded rapidly and margins are thin.

IT and electronics distribution is the clearest example for many Singapore buyers. Phones, memory products, processors, and other compact high-value goods can move through several entities quickly, sometimes with pre-arranged purchase and resale instructions. Scrap metal and commodity-style trades can raise similar issues where high values, unclear goods movement, and thin documentation sit together. The sector alone does not prove risk, but it changes how much evidence AP should expect before approval.

Recent enforcement activity makes the point concrete. In 2025, IRAS announced major MTF prosecutions involving alleged fictitious transactions and very large GST amounts, including cases reported at S$181 million and S$114 million. A 2024 conviction involved a S$55 million MTF arrangement. An AP team does not need to analyse those cases like a lawyer, but it should recognise the pattern: paper transactions, invoices, and GST claims can look orderly while the commercial substance is weak.

Heightened controls should be proportionate and specific. For a higher-risk prescribed-goods supplier, AP and finance leadership may require senior approval, stronger verification of the supplier representative, clearer evidence of goods movement, proof of warehouse or logistics handling, review of delivery route, and closer scrutiny of payment instructions. If the supplier was recently incorporated or recently GST-registered, the file should show why the buyer still considered the transaction commercially credible.

Customer Accounting for Prescribed Goods sits nearby because it was introduced to reduce GST fraud risk in prescribed goods supply chains. For buyer-side mechanics, the separate guide to Singapore customer accounting for prescribed goods is the better place to handle how that regime works. In an MTF due-diligence file, CAPG is a risk-context signal: if the transaction touches prescribed goods, the AP control should acknowledge the regime and show that the invoice treatment, supplier profile, and supporting evidence were reviewed together.

Lower-risk sectors should not copy the full burden mechanically. A small office-services supplier with a stable history, consistent GST status, ordinary pricing, and clear delivery evidence does not need the same file as a new electronics trader issuing high-value invoices. The practical standard is risk-based: the more the transaction resembles an MTF-prone supply chain, the more the buyer should document before approving payment and input-tax support.

When red flags fire, pause payment and document the decision

A red flag does not prove Missing Trader Fraud. It does mean the invoice should stop moving on autopilot. The safest operational response is to pause payment, keep the input-tax claim out of routine processing where appropriate, and resolve the evidence gap before the transaction is approved.

The first step is to define the issue precisely. "Supplier looks suspicious" is too vague to manage. "Supplier was incorporated two months ago, GST registration is recent, goods description says assorted electronics, no delivery note was provided, and payment is requested to a third-party account" is actionable. AP can then ask targeted follow-up questions rather than sending a broad request for "more documents".

Useful questions are tied to the missing evidence:

• Who arranged the trade and who at the supplier is authorised to deal with the buyer?
• Where did the goods come from, and where were they delivered?
• Which delivery note, warehouse receipt, or logistics record supports the movement?
• Why does the supplier's registered business activity differ from the goods on the invoice?
• Why is payment requested to an account that does not match the approved supplier master?
• Why is the GST registration date close to the invoice date?
• What contract, quotation, or order confirmation supports the price and margin?

If the counterparty is vague or evasive, commercial pressure should not push the invoice through. A legitimate supplier may need time to retrieve documents, but it should be able to explain the transaction in ordinary business terms. Refusal to identify the representative, provide delivery evidence, or explain payment instructions should be recorded as part of the decision.

AP's role is to identify the exception and preserve the record. Finance, tax, compliance, legal, or external advisers should decide whether to proceed, reject the transaction, terminate the relationship, make a report, or cooperate with IRAS if the business is approached. For a smaller company without separate tax or compliance teams, the escalation path may be the finance manager, director, and external accountant. The principle is the same: the person approving the risk should be named in the file.

The final note should say what happened. Payment held pending documents. Supplier provided delivery proof and finance approved. Supplier failed to respond and transaction rejected. Matter escalated to external tax adviser. Those short conclusions are more useful than a long narrative prepared later, because they show the buyer treated the red flags as decision points at the time.

Keep MTF controls separate from BEC, CAPG, and ordinary invoice validation

MTF due diligence should sit beside other AP controls, not disappear into a generic fraud checklist. Business email compromise and supplier bank-detail fraud usually test whether the payment instruction is trustworthy. MTF tests whether the supplier transaction and GST input-tax claim sit inside a fraudulent supply chain. Both matter, but they look for different evidence.

That distinction affects the file. Bank-detail controls focus on call-backs, change-request verification, payment approvals, segregation of duties, and unusual beneficiary accounts. MTF controls focus on supplier substance, goods movement, invoice support, GST registration, transaction pattern, and the buyer's documented response to risk indicators. A strong process for accounts payable fraud detection controls helps reduce payment loss, but it does not by itself show that the buyer considered the Knowledge Principle for a GST-bearing purchase.

The same boundary applies to other Singapore compliance checks. A valid UEN and GST registration support the supplier file, but they do not prove that a particular supply took place. A compliant tax invoice supports the input-tax claim, but it does not answer every question about commercial substance. The receipt channel sits in the same category: even when a supplier is set up to send Peppol invoices into Xero or QuickBooks via an InvoiceNow access point, structured delivery confirms format and routing, not the underlying commercial substance the Knowledge Principle is asking about. CAPG may change the GST accounting treatment for prescribed goods, but it does not replace the buyer's need to understand why a supplier, invoice, delivery, and payment instruction make sense together. The same logic applies when a Singapore buyer needs to self-account for GST on foreign supplier invoices under reverse charge: the RC mechanics handle the tax treatment, but the underlying supplier and transaction substance still require their own due-diligence record.

The operating standard is simple to state and demanding to maintain: when a suspicious GST-bearing supplier invoice is approved, the buyer should be able to retrieve one coherent transaction file. That file should show the onboarding checks, invoice evidence, red-flag assessment, escalation record, and approval conclusion. If the documents do not support that conclusion, AP has not finished its due diligence.