TL;DR: HST feels simple — collect it, remit it — which is exactly why it produces so many expensive mistakes. The costly ones: treating collected HST as your money, registering late and losing input tax credits, claiming ITCs without the documentation to defend them, charging the wrong rate to out-of-province customers, claiming full ITCs on meals, missing the rules on your industry’s quirks, and filing late when you can’t pay. Every one of these is cheaper to prevent than to fix.
HST is the tax businesses interact with most often and think about least. It runs in the background — the platform calculates it, the bookkeeper files it, the number goes out quarterly. Until a filing is late, a reassessment lands, or a cash crunch reveals that the “HST account” was spent in July.
Here are the seven mistakes that cost real money, roughly in order of how often we see them.
1. Spending the CRA’s money
The HST you collect is not revenue. It was never yours. You are holding it in trust for the CRA between the sale and the remittance — and the CRA treats it that way, with collection powers to match, including the ability to pursue directors personally for unremitted amounts.
The businesses that get hurt here aren’t dishonest. They’re busy. HST lands in the same bank account as everything else, the balance looks healthy, decisions get made against it, and then the quarterly remittance is due against money that’s gone.
The fix is mechanical: a separate savings account, with a percentage of every deposit moved automatically. The businesses that do this never have an HST crisis. It’s that simple and that boring.
2. Registering late — and paying tax you could have recovered
Registration becomes mandatory once taxable sales pass $30,000 over four consecutive calendar quarters. Two expensive versions of this mistake:
- Blowing past the threshold without noticing. You were required to start collecting and didn’t. The CRA can assess you for HST you never charged — which, since you can’t retroactively bill customers, comes straight out of your margin.
- Waiting until forced. Until you register, you can’t claim input tax credits — so every dollar of HST you pay on equipment, inventory, software, rent, and startup costs is simply lost. Businesses with real expenses and growth plans usually should register before the threshold, voluntarily.
3. Claiming ITCs you can’t defend
Input tax credits are where audits go first, because it’s where sloppy records are easiest to find. The rules require actual documentation — invoices with the supplier’s HST registration number on purchases above small thresholds — not just a line on a credit card statement.
Common failures: claiming ITCs from statements without invoices, claiming on expenses with a personal component, and claiming on amounts paid to unregistered suppliers (that contractor who charged you “tax” and pocketed it — your ITC is gone if their number isn’t real). An audit that disallows two years of undocumented ITCs, plus interest, is one of the most avoidable bills in Canadian small business.
The fix: receipt capture that actually files the source document — tools like Dext make this nearly automatic — and a rule that no ITC gets claimed without one.
4. Charging your rate instead of your customer’s
Place-of-supply rules mean you generally charge based on where your customer is, not where you are. An Ontario business charges 13% to Ontario customers, 5% to Alberta, 15% to the Maritimes — and BC, Saskatchewan, Manitoba, and Quebec layer their own provincial systems with separate registration rules on top.
Service businesses and e-commerce sellers hit this constantly. Charge 13% to everyone and you’re overcharging some customers and creating a mess; charge it to no one out of province and you’re building a liability. If you sell across provinces, this needs to be configured properly once and checked when you enter new markets.
5. Full ITCs on meals and entertainment
Small but universal: meals and entertainment are generally 50% deductible, and the ITC claim is limited to match. Books that claim 100% of the HST on every restaurant receipt are quietly building a reassessment adjustment. It’s rarely a huge number — it’s just present in almost every file that hasn’t been professionally reviewed, and it’s the kind of easy finding that invites an auditor to keep digging.
6. Missing your industry’s quirks
Generic HST knowledge fails at the edges, and every industry has edges:
- Construction: HST on holdbacks generally isn’t payable until the holdback is due — invoice it wrong and you’re remitting tax on money you haven’t collected.
- Health & wellness: exempt core services mean no ITCs on related costs, while product sales and some third-party work are taxable — mixed clinics need the streams separated.
- E-commerce: marketplace rules mean Amazon may collect on some sales while your Shopify store remains fully your responsibility.
- Real estate: new builds and substantially renovated properties can attract HST on sale — a six-figure surprise for the unprepared flipper.
If any of those sentences describes your business and surprises you, that’s worth a conversation this month, not eventually.
7. Not filing because you can’t pay
When cash is tight, some owners hold the return, reasoning that filing announces a debt they can’t cover. This is exactly backwards. Late filing adds penalties on top of the interest you’d owe anyway — and unfiled returns are the fastest way to turn the CRA from a creditor into an adversary, freezing refunds and escalating collections.
File on time, always. If you can’t pay, the CRA negotiates payment arrangements far more readily with a business that files reliably than one that goes dark.
Frequently asked questions
What happens if I passed $30,000 and never registered?
You were required to register and collect from the point the threshold rules kicked in, and the CRA can assess you for the uncollected tax. The right move is to get registered and address the gap proactively — voluntary disclosure can reduce penalties. What doesn’t work is waiting to be found.
How long do I need to keep receipts for ITC claims?
Six years from the end of the tax year, and “keep” means the actual invoice showing the supplier’s registration number where required — not just the bank line. Digital copies are fine; capture tools make this painless.
Should I use the Quick Method?
The Quick Method lets eligible smaller businesses remit a flat percentage of sales instead of tracking ITCs, and for low-expense service businesses it can genuinely save money and admin. For anyone with significant taxable costs, it usually costs more than it saves. It’s a calculation — run it, don’t guess.
Which provinces do I charge what?
As a general map: 13% HST for Ontario customers, 15% for the Maritime HST provinces, 5% GST for Alberta and the territories, and 5% GST plus separate provincial regimes for BC, Saskatchewan, Manitoba, and Quebec — each with its own registration rules once you’re meaningfully selling there. Configure it once, verify when you expand.
Can the CRA really come after me personally for HST?
Yes. Unremitted HST is trust money, and directors can be held personally liable for a corporation’s failure to remit. It’s one of the few business debts that routinely pierces the corporate shield — which is precisely why the separate-account habit in mistake #1 matters.
Most HST problems are structural: a missing account, a missing habit, a setting nobody configured. All of it is fixable, and prevention costs a fraction of a reassessment. YBL handles HST as part of the full picture for Canadian businesses — registration strategy, clean ITC records, correct multi-province setup, and filings that go out on time every time. If any mistake on this list felt familiar, let’s talk before the CRA does.