Crossed $30,000 without registering for GST/HST? The CRA can back-date registration and assess tax you never charged, plus penalties and interest.
Applies in: across Canada
Nobody gets a letter the day they cross $30,000. The CRA does not watch your sales in real time, and plenty of Canadian businesses drift past the GST/HST threshold without noticing — a good quarter becomes a good year, and registration stays on a to-do list that never gets done. The trouble is that the obligation is automatic. When it surfaces, and it usually does, the bill is calculated from the day you should have registered, not the day you did.
This page explains how that plays out: the back-charging, the penalties and interest, and the one program that can cut them down. If you have not crossed the threshold yet and just need the sign-up, go straight to our guide on how to register for GST/HST in Canada. If you are still under $30,000 and deciding whether to register early, our GST number guide for sole proprietors covers the voluntary case.
The CRA's small supplier rules fix your effective date of registration by your sales pattern, not by your application:
Miss those dates and nothing pauses. Every taxable sale from your effective date carries GST/HST in the CRA's eyes — 5 percent GST, or the HST rate for the customer's province under the place-of-supply rules — whether your invoice said so or not.
Taxi and ride-share drivers get no threshold at all: registration is required from the first fare.
Sometimes nobody finds out for years, which is exactly what makes the eventual bill bigger. The usual triggers:
None of this requires bad intent on your part. The assessment machinery treats an honest miss and a deliberate dodge the same way at first; what distinguishes them is how you respond once you know.
When the gap is opened up, the CRA assesses each missed reporting period on a net tax basis:
Tax you were required to charge on your taxable sales from the effective date, minus input tax credits for GST/HST you paid on business expenses in the same periods, plus penalties, plus interest.
Two parts of that deserve attention. First, the tax on sales you never charged tax on. If your customers paid a flat $1,000 for a job, the CRA's default under its policy statement P-118R is a tax-extra assessment: the $1,000 counts as the consideration for the supply, and the tax is calculated on top of it. Only where the facts show the price was understood to include the tax does the CRA assess on a tax-included basis, carving the tax out of what you received. Either way, the money comes out of your margin. Asking customers to top up invoices from two years ago is theoretically possible and practically a dead end for most businesses.
Second, the input tax credits are real money in your favour, and they depend entirely on your records. The GST/HST you paid on equipment, materials, subcontractors, rent, and software during the gap periods offsets the tax on your sales, period by period. A business with heavy expenses can see its assessment cut substantially. A business with no receipts cannot claim what it cannot document — the CRA's input tax credit rules require the invoice information for each claim to be on hand before the claim is made. The credits also run on their own clock: for most registrants, an ITC must be claimed in a return filed within four years after the end of the reporting period in which it could first have been claimed.
On top of net tax:
Penalties for GST/HST are not deductible expenses — section 67.6 of the Income Tax Act bars deducting a fine or penalty imposed under a law, as the CRA's folio on the deductibility of fines and penalties sets out. The arithmetic lesson is dull and reliable: every month of delay adds interest and risks another penalty, and filing stops most of the bleeding even if paying takes longer. Our GST/HST return filing guide covers the mechanics of the returns themselves.
If you have discovered the gap yourself, the sequence matters:
The VDP exists for exactly this fact pattern: a taxpayer who comes forward, before enforcement finds them, and discloses completely. The CRA revised the program effective October 1, 2025 — the current rules are in GST/HST Memorandum 16.5-1 — and the current structure has two tiers:
Conditions apply. The disclosure must be complete — every period, every error — and must include the returns and records for at least the most recent four years of non-compliance. The tax itself is never relieved; only penalties and a share of interest are. And the timing is unforgiving in one specific way: once the CRA has started an audit or investigation into the account, the door closes. The value of the VDP is highest precisely when the gap is freshest in your own mind and the CRA has not yet noticed. For anything beyond a simple one-or-two-period miss, an accountant's hour to structure the application is cheap insurance against a declined disclosure.
Do not register with a false recent effective date and hope the past stays past — the mismatch between your income tax revenue and your GST/HST history is the first thing a review checks. Do not start charging customers GST/HST before your registration is effective; charging tax without being a registrant creates its own problems, and amounts collected as tax must be remitted. Do not ignore a CRA demand letter: the $250 penalty is the smallest of your worries, since a demand ignored is how files move from correspondence to audit.
And do not treat this as only a GST/HST problem going forward. Once registered, the habits that prevent a repeat are simple: track taxable sales quarterly so the $30,000 test never ambushes you again, file every return on time even in a nil period, and keep the expense receipts your input tax credits depend on. Our guide on how to charge GST/HST covers the day-to-day rules once you are registered.
| Tax you should have charged | Assessed back to your effective date of registration |
|---|---|
| Failure-to-file penalty (per late return) | 1% of amount owing + 0.25% per month, up to 12 months |
| Penalty if CRA demands a return and you still do not file | $250 per return |
| Interest | Prescribed rate, compounded daily, from each due date |
Per the Canada Revenue Agency's published penalty and interest rules for GST/HST. Input tax credits on your business expenses reduce the net amount assessed — keep your receipts.
The obligation does not wait for your paperwork. Once you stop being a small supplier, the CRA treats you as a registrant from your effective date of registration. When the gap is found, the CRA can assess the GST/HST you should have charged on your taxable sales from that date forward, add failure-to-file penalties and interest, and require returns for every missed period. Registering late does not erase the back periods — it starts the process of settling them.
It depends how you crossed the line, under the CRA's small supplier rules. If a single calendar quarter's taxable sales exceeded $30,000, your effective date is the day of the supply that put you over, and you must charge tax on that very supply; you have 29 days from that day to apply. If you crossed $30,000 over four consecutive calendar quarters (but not in one quarter), you stop being a small supplier at the end of the month after that quarter, and your effective date is the first supply after that. Either way, the effective date is set by the sales, not by when you got around to filing the form.
Yes. That is the expensive part. The tax is calculated on the taxable sales you made from your effective date, whether or not your invoices mentioned GST/HST. In practice the amount is worked out from your recorded revenue. The CRA's default, under its policy statement P-118R, is a tax-extra assessment: what you charged counts as the consideration, and the tax is calculated on top of it. Only where the facts show your price was understood to include the tax does the CRA assess on a tax-included basis and carve the tax out of the total. Going back to customers to collect it after the fact is rarely practical, so the cost usually lands on the business.
Yes, and they are the main thing that softens an assessment. For each back reporting period, your net tax is the GST/HST you were required to charge on sales minus the input tax credits (ITCs) for GST/HST you paid on business expenses in that period. This is why keeping receipts and invoices for the gap years matters — undocumented expenses generally cannot support an ITC claim, and missing ITCs are money left on the table.
Under the CRA's published rules, a return filed late with an amount owing draws a failure-to-file penalty of 1 percent of the amount owing, plus 0.25 percent of the amount owing for each full month the return is late, up to 12 months. If the CRA issues a demand to file and you still do not, there is an additional $250 penalty per return. Interest at the prescribed rate, compounded daily, runs on amounts owing — and penalties themselves are not tax-deductible.
Prosecution is the far end of the spectrum and is aimed at deliberate evasion — for example, collecting GST/HST from customers and keeping it without registering or remitting. Ordinary late registration by a business that crossed the threshold and did not notice is normally handled as an assessment with penalties and interest. The distinction the CRA draws is between a compliance failure and a deliberate scheme; a voluntary disclosure, made before the CRA contacts you, also comes with relief from prosecution for what you disclose.
Yes — a failure to register when required is one of the situations the CRA's Voluntary Disclosures Program (VDP) is built for. You come forward, register, and disclose the back periods completely. Under the revised program in effect since October 1, 2025, an unprompted disclosure (you apply before the CRA contacts you about the issue) can receive 100 percent penalty relief and 75 percent interest relief; a prompted disclosure can receive up to 100 percent penalty relief and 25 percent interest relief. The tax itself is still owed — the relief is on the penalties and part of the interest.
GST/HST assessments are generally limited to four years after the later of the day the return was required to be filed and the day it was actually filed — which is why unfiled periods stay exposed: for a return that was never filed, that later day has not arrived. And where the CRA finds a misrepresentation due to neglect, carelessness, wilful default, or fraud, it can reassess at any time for the periods the misrepresentation touches. The VDP's own relief is also time-bounded: penalty relief reaches back to periods that ended within the previous 10 years, and interest relief to interest accrued in the previous 10 calendar years.
Register now, with the correct effective date, and reconstruct the back periods: your sales totals, and every expense receipt that supports an input tax credit. Then decide, ideally with an accountant, whether to file the back returns directly or to apply under the Voluntary Disclosures Program first — once the CRA contacts you, the better VDP tier is gone. Our registration guide walks through the sign-up itself, step by step.
More strictly. Taxi businesses, including ride-share drivers, must register for GST/HST from their first taxable supply — the $30,000 small supplier threshold does not apply to them at all. A driver who has been taking fares unregistered has no threshold defence, which makes the back-assessment mechanics on this page apply from day one of driving.