Most owners treat a vendor invoice as proof of everything printed on it. Auditors do not. This guide covers where the verification duty comes from, how to run the check in under a minute, and what to do when a number fails.
Key Takeaways
- Once a purchase reaches $100, the supplier’s registration number becomes mandatory documentation, not a courtesy.
- A genuine number belonging to a different business fails just as badly as an invented one.
- The lookup needs nine digits, the registered name, and your transaction date.
- Good faith is no defence, so save dated proof of every check you run.
Why an Invalid Supplier GST/HST Number Kills Your ITC Claim
Subsection 169(4) of the Excise Tax Act, the statute behind the goods and services tax and the harmonized sales tax, makes documentation a precondition of the claim to input tax credits (ITCs). Before you file, you must already hold information satisfying the Input Tax Credit Information (GST/HST) Regulations, and those requirements scale with the purchase:
| Purchase total | What your records must show |
|---|---|
| Under $100 | The vendor’s name, or the name it does business under, plus the date and the tax |
| $100 to under $500 | Everything above, plus the vendor’s registration number |
| $500 or more | Everything above, plus your name, payment terms, and a description of the supply |
Every business in Canada purchasing goods or services from registered vendors claims these credits on the strength of that nine-digit number. Above the lowest tier, it is a condition of the credit. Carry a wrong one and the claim fails on documentation alone, before anyone asks whether the expense was commercial. Our guide to HST for small business covers the wider documentation these tiers demand.
Input tax credits only include tax that a registrant had authority to charge, and your honesty is irrelevant here. In Comtronic Computer Inc. v. The Queen (2010 TCC 55), a vendor supplied numbers that were validly issued but registered to other businesses. The Tax Court denied roughly $500,000 of credits because the buyer never confirmed them.
What that costs. Priya’s contractor bills her $4,520 plus $587.60 of Ontario sales tax, quoting a number that belongs to an unrelated numbered company. CRA denies the $587.60 and adds interest. Across eleven such billings, the assessment reaches $6,463 on work that genuinely happened.
How to Use the CRA Registry to Check a GST Number
The GST/HST Registry is a free online tool on canada.ca that confirms rather than searches. You cannot type a company name and discover its account. You supply what you already have:
- Enter only the first nine digits of the account number, which are the supplier’s CRA business number, dropping the RT0001 suffix.
- Enter the company name exactly as the Agency holds it, punctuation included.
- Enter the date of your transaction: the date on the receipt, contract or bill.
- Read the result, which confirms the registration status on that specific day.
That date field matters, because GST registration is not permanent. A vendor can deregister, so a number that verified cleanly in March may fail for a December purchase. Always check the day you actually transacted.
Name Mismatches Cause Most GST Verification Failures
Most failed lookups are not fraud. They are name problems. A restaurant trades as “The Corner Kitchen” while its corporate name is “1234567 Ontario Inc.” Enter the wrong version and you get nothing back, which looks identical to an unregistered vendor.
So work through the mismatch first. Try the name on the bill, then the registered name, then any operating name shown on a cheque. If none land, ask the vendor for the exact legal business name they gave the Agency, or call the Canada Revenue Agency’s business enquiries line at 1-800-959-5525. The CRA website lists both tools.
What to Do When a GST Account Number Fails
A failed check is a payment decision, not only an accounting one. Take these steps in order:
- Pause the tax portion of the payment, settling the goods or services but holding the sales tax.
- Ask for a corrected invoice showing the right number and the name on file.
- Re-run the check against the corrected details and the original transaction date.
- If the vendor is not a registrant, they cannot charge GST or HST at all, even on fully taxable goods or services. Ask for a reissued bill. Remember that a supplier must register once taxable revenue over four consecutive calendar quarters passes $30,000, so a missing number can also flag a vendor who should have registered.
- Claim nothing until it resolves, because an unsupported ITC costs more than a delayed one.
Already paid tax to someone who was never registered? Ask that vendor for a refund or credit note first. When that fails, a rebate application on Form GST189 is the fallback, filed within two years of paying.
How to Document Your HST Number Checks for a CRA Audit
Verification you cannot prove is verification you did not do. Save each number validation as a PDF beside the paperwork it supports, capturing the number checked, the name used, the transaction date entered, and the date you ran it. The Excise Tax Act requires you to keep those records for six years, the same retention period already applying to your books.
In our CRA representation practice, this is exactly where CRA audits open. The auditor asks for your credit schedule, runs every vendor number through the registry in bulk, then arrives with the exceptions already listed. Owners who hand back dated confirmations close them in one exchange. Owners who cannot spend weeks chasing counterparties who have moved on. If a review letter already flags your credits, our audit representation team handles that conversation.
How to Simplify Verification for QST and Recurring Suppliers
Checking every bill is unnecessary. Checking every supplier is not, because even suppliers who are registered today can deregister tomorrow. Verify supplier registration at onboarding, verify again once a year, and verify immediately whenever a vendor changes its name, its banking details, or its billing template. Those changes tend to precede a bad number.
A province with its own provincial sales tax adds a step, and a selected listed financial institution follows its own set of rules entirely. Quebec keeps its own system: vendors there carry a QST registration number administered by Revenu Québec through a separate lookup, and a valid federal GST account tells you nothing about the QST number.
You can also shrink the problem. Businesses using the Quick Method of accounting do not claim input tax credits on most operating costs, so verification narrows to capital purchases.
A second example. A Vaughan agency ran $180,000 of subcontractor billings through one vendor and claimed $23,400 of Ontario tax. That vendor deregistered in July, so the $11,200 claimed afterwards died while the earlier credits survived. One annual re-check would have caught it.
Frequently Asked Questions
How can I check if a GST/HST number is valid?
Use the Agency’s registry and enter the nine-digit business number portion of the account, the exact supplier’s name on file, and your transaction date. It confirms whether the business is registered on that day. It cannot find a number from a company name alone.
Can I verify a supplier’s number for free?
Yes. The registry is a free public service with no sign-in. Paid services exist for high-volume payables, though they query the same data, so cost never justifies skipping the check. Note that only a business registered for the normal GST/HST appears; simplified digital-economy registrants do not. If you were charged tax on services from a business listed on the CRA’s simplified registrant list, no ITC is available; ask that vendor for a refund instead.
What happens if the supplier was not registered on my transaction date?
Your claim fails, because the vendor had no authority to charge the tax. The Agency reassesses the credit and adds interest from the period you claimed it. Recovery becomes a commercial matter with that vendor.
Does the name on an invoice have to match tax records exactly?
For the lookup, yes. The registry matches the name on file, often the corporate name rather than the trade name on your bill. If the printed version fails, ask for the exact legal name the vendor registered.
How often should I verify supplier numbers?
Once at onboarding, once a year afterwards, and again whenever a name, ownership or banking detail changes. Registration can lapse quietly, and the lookup is where that surfaces first.
The Bottom Line
Verification is one of the cheapest controls in a business: under a minute, no cost, and it protects ITCs that routinely run into five figures.
- Registration numbers are mandatory documentation above $100, and wrong ones fail like missing ones.
- Check nine digits, the exact name, and the real transaction date, every time.
- Save dated proof and keep it beside the bill for six years.
- Hold back the tax portion until a failed number resolves.
Supplier verification looks simple until an auditor works backwards through three years of payables. Your vendor mix and claim volume change what a sensible control looks like, so treat this as a starting point rather than a ruling on your file. Get in touch with our team to review how your documentation would hold up.
