The tax problems that sink new Canadian businesses are rarely exotic. They cluster around a handful of predictable mistakes, made by honest owners who simply did not know the rule or assumed it would not apply to them. The good news is that because the mistakes are predictable, they are avoidable. Here is the list we see most often, drawn from years of representing business taxpayers in audits, objections, and the Tax Court of Canada.
Mistake 1: Assuming a corporation makes you a contractor
Many businesses ask their workers to incorporate, and many workers assume that having a corporation settles their status as an independent contractor. It does not. The Canada Revenue Agency looks past the corporation to the substance of the relationship, weighing factors such as the worker's financial risk, the client's control over what work is done and how, who provides the tools, and whether the worker could send a replacement. If a corporation sends the same person every day to do the same work, alongside the client's employees, under the client's direction, the agency can treat it as a "personal services business." The consequences are severe: the corporation loses the small business deduction, and most of its deductions are denied, almost as if the corporation never existed. Workers in industries that push incorporation, such as trucking, are especially exposed and should get advice before assuming the corporate form protects them.
Mistake 2: Mischaracterizing employees as contractors
The same employee-versus-contractor analysis cuts the other way for businesses that hire. Calling a worker a contractor does not make them one. As the saying goes, if you paint a duck to look like a camel and label it "camel," the agency will still see webbed feet and hear quacking and declare it a duck — and may impose penalties at the same time. If the Canada Revenue Agency reclassifies your contractors as employees, you can face assessments for unremitted source deductions plus penalties and interest. The factors that point toward genuine contractor status include the worker bearing financial risk, controlling how the work is done, supplying their own tools, and being free to hire a helper or send a substitute. Document the relationship with a proper agreement and make sure the reality matches the label. The misclassification can be challenged, but it is far better to get it right at the outset.
Mistake 3: Missing the $30,000 HST threshold
One of the most common and costly oversights is failing to register for and charge GST/HST after crossing the $30,000 annual revenue threshold. Owners who do not realize they have passed it keep invoicing without tax — and then learn during an audit that they owe, say, 13% HST on all those sales, even though they never collected a cent of it from their customers. The Canada Revenue Agency wants its tax regardless. Register for an HST number, watch your revenue against the threshold, and apply the correct destination-based rate to every transaction. The upside of registering early is access to input tax credits on the HST you pay on your own expenses.
Mistake 4: Spending trust money
This is the mistake that turns a business problem into a personal catastrophe. GST/HST you collect and the income tax, CPP, and EI you withhold from employees are trust funds — they belong to the government, not to the business. When cash is tight, the temptation is to use that money to pay rent, staff, or suppliers. Doing so exposes the directors personally: unremitted trust amounts pierce the corporate liability shield and can be assessed against directors for up to two years after they last served. The defence — that a reasonable director would have done the same — is hard to win, because the agency tends to apply a near-impossible "perfect director" standard. The safest practice is to never treat trust money as available cash; outsourcing payroll so the remittances leave automatically removes the temptation entirely.
Mistake 5: Paying dividends ahead of corporate tax
Corporate owners who pay themselves dividends sometimes forget to leave enough in the company to cover its corporate tax at year-end. If a corporation pays dividends to shareholders while it has unpaid corporate taxes, a collections officer can assess the dividend recipients for that unpaid tax — clawing the dividend back into the government's hands. Whether you pay yourself by salary or dividends, plan the corporation's cash so its own tax bill is funded first.
Mistake 6: Estimating the deductions auditors love to deny
Three expense categories are low-hanging fruit for auditors because owners so often estimate them rather than document them:
- Vehicle expenses. Most small businesses just pick a business-use percentage, and auditors know it. The fix is a vehicle log: record each business trip with destination and start and end odometer readings, plus year-start and year-end odometer readings, so you can prove the percentage. Note that the Income Tax Act does not strictly require a mileage log to win a case in Tax Court — the log is an invention of the audit department — but having one keeps the dispute out of court in the first place.
- Meals and entertainment. Auditors want original receipts plus a record of the client and business purpose for each meal or ticket, and only 50% of a client meal is deductible (you can expense the client's meal, not your own). The casual practice of expensing the occasional dinner or game ticket that was actually personal is common — and not legal.
- Home-office expenses. Claiming an inflated square footage, or rooms that are not genuinely used for business, is a reliable way to attract scrutiny. Measure the real percentage, keep the supporting bills (property tax, mortgage, electricity), and document the space with photos and a floor plan in case you move before an audit.
Mistake 7: Treating non-filing as a way to avoid tax
Some owners who cannot pay their tax bill decide not to file at all. This is exactly backward. It is not illegal to be unable to pay; it is illegal not to file. Non-filing can escalate from penalties to criminal prosecution — and the Canada Revenue Agency's success rate on prosecutions it pursues is close to 100%. File on time even when you cannot pay in full, then pay down the balance as you can; filing on time avoids the late-filing penalty, and paying as soon as possible afterward limits the daily-compounding interest.
Mistake 8: Signing a waiver or talking too freely in an audit
If an auditor asks you to sign a waiver allowing a reassessment outside the normal reassessment period, do not sign it without legal advice — ever. And keep audit conversations narrow: an auditor may only demand information relevant to their job, so do not volunteer more than is required, and avoid casual chat that can hand them a thread to pull (a mention of a Hawaii trip can start an auditor wondering how you afforded it). Never let an auditor take your original documents, which can be lost and leave you unable to defend yourself later. These are small disciplines that prevent large problems.
How the work gets done
Most of these mistakes are cheap to avoid and expensive to fix after the fact. Barrett Tax Law can help you set your business up to sidestep them — and, where a mistake has already been made, represent you in the audit, file a notice of objection, and appeal to the Tax Court of Canada if needed. The first consultation focuses on your situation and the realistic options.
This guide draws on Dale Barrett's book, A Quick and Dirty Business Start-Up Guide. It is general information, not legal advice, and reading it does not create a lawyer-client relationship.