Small Business Tax Deductions Checklist (Ontario)

Most self-employed professionals and owner-managers don't overpay tax because they're doing something wrong — they overpay because they don't claim everything they're legitimately entitled to. Here are the deductions we see missed most often, and the records you need to support them.

Home office expenses

If you run your business from home, even part-time, a portion of your rent or mortgage interest, utilities, home insurance, and maintenance can be deductible, based on the percentage of your home used for business. This is one of the most under-claimed deductions among self-employed professionals — largely because owners don't track the calculation consistently year to year.

Vehicle expenses

If you use a vehicle for business — client visits, site inspections, picking up supplies — a portion of fuel, insurance, maintenance, and lease or loan costs can be deducted based on the percentage of kilometres driven for business purposes. The catch: you need a mileage log. Without one, this deduction is difficult to defend if the CRA ever asks.

Professional fees, dues, and subscriptions

Accounting and legal fees, professional association dues, industry subscriptions, and even some software subscriptions used for the business are generally deductible. This category is frequently under-claimed simply because owners don't think to add up smaller recurring charges throughout the year.

Insurance and benefits

Business insurance premiums — liability, professional, or business property insurance — are deductible business expenses. For incorporated business owners, there are also opportunities around health and dental benefits paid through the corporation that are worth reviewing with a CPA, since the right structure can make these more tax-efficient than paying for the same coverage personally.

Capital purchases and CCA

Equipment, computers, furniture, and vehicles purchased for the business generally can't be deducted all at once — instead, they're deducted gradually over time through Capital Cost Allowance (CCA). Many owners either forget to claim CCA at all, or don't realize that in the year of purchase, only a portion of the usual rate can typically be claimed. Getting this right matters both for this year's return and for the eventual sale or disposal of the asset.

The records that actually matter

• A mileage log, even a simple one, for any vehicle expense claim.
• A consistent home office percentage calculation, documented once and applied consistently.
• Receipts or statements for every capital purchase, including the purchase date, which determines how CCA is calculated in the first year.
• A separate business bank account or credit card, which makes every other record on this list dramatically easier to produce.

The deductions themselves are rarely the hard part. Having the records to support them, if the CRA ever asks, is what separates a clean tax return from a stressful one.