If you run a business or are self-employed in Canada, the single biggest lever on your tax bill is the set of expenses you claim. Every legitimate dollar of deductible expense reduces the income you pay tax on. The catch is that a deduction is only as good as your ability to support it if the Canada Revenue Agency (CRA) ever asks. This guide walks through how business deductions actually work, what the common categories are, and the record-keeping habits that keep your claims standing.
The basic rule: incurred to earn income, and reasonable
The foundation for business deductions is section 9(1) of the Income Tax Act, which defines profit as a net concept, and section 18(1), which limits what can be subtracted. In plain terms, you can deduct an expense if you incurred it for the purpose of gaining or producing income from the business — and only to the extent it is reasonable in the circumstances. Personal and living expenses are not deductible.
That "reasonable" qualifier matters. You do not get to deduct an extravagant version of an ordinary cost just because it touches the business. The question an auditor asks is whether the expense was genuinely part of earning your business income, and whether the amount makes sense for what was actually done.
The common deductible categories
The CRA recognizes a long list of ordinary business expenses. Among the categories most small businesses use:
- Advertising — including digital advertising and advertising in Canadian media.
- Bad debt — an account receivable you already reported as income but will not be paid.
- Business start-up costs — expenses that preceded operations, claimable in the fiscal period the expense was incurred.
- Business taxes, fees, licences, and dues — though not club dues where the club's main purpose is dining, recreation, or sport.
- Insurance — ordinary commercial premiums on buildings, machinery, and equipment used in the business (vehicle insurance is claimed as a motor-vehicle expense).
- Interest and bank charges — interest on money borrowed for business purposes, plus financing fees (some deducted over five years).
- Legal, accounting, and professional fees — including fees to prepare an objection or appeal against an assessment.
- Maintenance and repairs, rent, salaries and benefits, supplies, office expenses, telephone and utilities, delivery and freight — the everyday cost of operating.
- Travel — public transit, hotel, and meals incurred to earn business income (the 50% limit usually applies to the meal portion).
Small consumables — pens, stamps, paperclips, stationery — are deductible as office expenses. Bigger items like desks, chairs, filing cabinets, and calculators are capital items and are deducted over time through capital cost allowance rather than all at once.
Meals and entertainment: the 50% rule
Meals and entertainment are a frequent audit target because of how often they are over-claimed. The general rule is that only 50% of a qualifying meal or entertainment expense is deductible. The practical translation many owners forget: when you take a client to dinner, you can claim the meal — but the deductible portion is half, and you need to be able to say who the client was and what the business purpose was. Auditors routinely ask for the original receipts plus that context for each item; without it, they are happy to deny the expense.
Clothing is almost never deductible
A common misconception is that work clothing is deductible. As a rule, anything you could wear outside of work — including steel-toed boots — is treated as a personal expense and cannot be claimed. The narrow exception is genuinely specialized protective gear, such as a welding helmet or medical personal protective equipment. If it doubles as ordinary clothing, assume it is not deductible.
Original receipts beat statements
Here is a subtlety worth internalizing: while the Income Tax Act does not strictly require an original receipt to claim most business expenses, an auditor who asks for the original and is handed only a credit-card statement or a scan may disallow the expense anyway. Credit and debit statements show that money moved; they do not show what was bought or why. Keep the original invoices and receipts, and — because thermal receipts fade — keep a scan or photo as backup.
The categories auditors love
Two deduction categories draw scrutiny because they are so often estimated rather than measured: vehicle expenses and home-office expenses. Both are covered in detail in companion guides, but the headline is the same for each — the deduction is fine, the estimate is the problem. Auditors jump on round-number guesses. A vehicle log and a measured home-office percentage turn a soft claim into a defensible one.
Turning a hobby into a side hustle
If you do not have a business, you may be leaving deductions on the table. Many hobbies can become a modest side business — if you enjoy 3D printing, a part-time print operation lets you deduct the printer, filament, and a share of home-office costs; if you love to cook, a small catering business lets you deduct equipment you also use yourself. The point is not to manufacture a fake business but to recognize that genuine income-earning activity unlocks genuine deductions. The income has to be real and the deductions have to be tied to earning it.
Keep your records for six to seven years
As a general rule, keep business records for at least six years from the end of the tax year to which they relate. Even though the CRA usually reassesses personal and corporate returns only three or four years back, it can reach further back where it suspects fraud or gross negligence — so keeping records a year or two beyond the minimum is cheap insurance. Some records should essentially never be discarded: purchase and sale agreements, share transactions, and registries needed to compute a capital gain on a future disposition.
Putting it together
The discipline that produces a low, defensible tax bill is unglamorous: claim every expense you genuinely incurred to earn income, keep the amounts reasonable, and hold onto the paper that proves it. For related strategies, see our guides on vehicle and home-office deductions and income splitting for owner-managers.
This guide draws on Dale Barrett's book Pay WAY Less Tax!, a plain-language collection of tax-saving tips and strategies for Canadians. The book is general information, not legal advice; the rules change often, so confirm the current treatment for your own situation before acting.