Construction Tax Write-Offs: What Contractors Can and Cannot Claim
The write-offs available to Ontario construction companies, the expense versus capital line that decides how you claim them, the trade-specific deductions most contractors miss, and the claims the CRA denies most often. Written by a licensed Canadian CPA who works with contractors.
A construction company can write off any reasonable cost incurred to earn business income: materials, subcontractors, wages, tools, equipment, vehicles, site costs, insurance, WSIB premiums, permits and professional fees. The question is rarely whether a cost is deductible, but how and when. An expense is claimed in full this year; a capital cost is claimed over several years through capital cost allowance. Getting that line wrong, and keeping records that cannot support the claim, is where contractors lose deductions.
The Question Is Usually When, Not Whether
Most contractors ask whether something is deductible. The more useful question is how and when. The CRA's basic test is straightforward: an expense is deductible if it was incurred to earn business income and is reasonable in the circumstances. Materials, subtrades, wages, tools, site costs and insurance clear that test comfortably.
The difficulty sits one layer down. A cost that clears the deductibility test still has to be classified correctly, because a genuine business cost claimed in the wrong year, or in the wrong way, gets denied just as firmly as a personal one. Construction has more of these classification decisions than most industries: equipment against tools, subcontractors against employees, repairs against upgrades, holdbacks against revenue. For the wider picture please see our construction CPA services.
Expense or Capital: The Line That Decides Everything
This is the single most consequential distinction on the page. An expense is consumed in the year and comes off your income in full. A capital cost buys something with lasting value, and you deduct it over several years through capital cost allowance instead.
| Factor | Expense (deduct now) | Capital (deduct over time) |
|---|---|---|
| What it buys | Something consumed in the year | Something with lasting value |
| Deduction | Full amount this year | Capital cost allowance over several years |
| Tools | Small hand tools, consumables, blades | Larger equipment with a useful life |
| Work on an asset | Repair that restores it to working order | Upgrade that improves or extends it |
| Vehicles | Fuel, insurance, repairs, licensing | The vehicle itself, subject to the ceilings |
| Getting it wrong | Overstates this year's deduction | Understates it, and misstates the asset |
Contractors err in both directions. Expensing a $30,000 excavator overstates the current year and misstates the balance sheet a lender or bonding company will read. Capitalising a box of blades understates the deduction and creates an asset that does not exist. The classification also follows through to the disposal years later. Please see our capital cost allowance guide.
The Write-Offs Specific to Construction
Every business deducts rent, phones and professional fees. These are the ones that belong to the trade, and where the money and the exposure actually sit.
| Write-Off | Treatment | What Contractors Get Wrong |
|---|---|---|
| Subcontractor payments | Deductible, usually the largest single cost | Missing the T5018, or the CRA recharacterising the subtrade as an employee |
| Materials | Deductible, costed to the job | Sitting in overhead, so job margins are fiction |
| Tools and equipment | Small tools expensed, larger equipment capitalised | The line between the two, in both directions |
| Vehicles and fuel | Deductible at business-use percentage, caps apply to passenger vehicles | 100% claims with no logbook, and missing the passenger vehicle caps |
| WSIB premiums | Deductible in the year | Not the deduction, but unregistered subtrades creating liability |
| Safety gear and PPE | Deductible | Claiming ordinary clothing alongside it |
| Site costs, trailers, storage | Deductible, costed to the job | Left in overhead rather than allocated |
| Permits and licences | Deductible | Not costed to the job that required them |
| Meals on site | Generally 50% deductible | Claimed in full |
| Training and certifications | Deductible where it maintains existing skills | Claiming training that qualifies you for a new trade |
The T5018 catches more contractors than any other single filing. Where construction is your principal business activity and you pay subcontractors for construction services, the Contract Payment Information Return is required, separately from your T2, with its own deadline and its own penalties. Many contractors have never filed one.
Subcontractors: The Largest Deduction and the Largest Risk
Subcontractor payments are usually a contractor's biggest write-off, and they are fully deductible. The risk is not the deduction itself but what sits behind it. If the CRA reviews the relationship and concludes a subcontractor was really an employee, the consequences reach well past the deduction: unremitted source deductions, both employer and employee portions, plus penalties and interest, and potentially WSIB exposure on the same facts.
The test is a question of fact, weighing control, ownership of tools, chance of profit and risk of loss, and the overall relationship rather than what the invoice says. Calling someone a subcontractor does not make them one. Please see our subcontractor versus employee guide and our WSIB compliance guide.
Costing Write-Offs to the Job
A deduction that lands in general overhead is still deducted, so the tax result is the same. The management result is not. Materials, site costs, permits and fuel sitting in a single overhead bucket mean your job margins are guesswork, and the jobs that consumed the most usually look the most profitable. Allocating costs to the jobs that caused them is the difference between knowing which work makes money and believing you do. Please see our construction bookkeeping.
What Gets Denied
The pattern is consistent, and none of it is subtle.
- Personal costs run through the business. The family vehicle, the home renovation materials, the meals that were not business. These are found quickly and they colour everything else in the file.
- Vehicle claims with no logbook. A business-use percentage with no record behind it is an assertion, and 100% on a truck that goes home each night is rarely plausible.
- Capital purchases expensed in the year. The equipment is deductible, just not all at once, and the correction moves income between years with interest attached.
- Expenses with no invoice. A bank statement shows a payment, not what was purchased. Without the invoice the expense is not supportable regardless of how legitimate it was.
Where construction write-offs go wrong: personal costs in the business, 100% vehicle claims with no logbook, capital purchases expensed in full, meals claimed at 100% rather than 50%, ordinary clothing claimed as safety gear, subcontractors who are really employees, and expenses with nothing behind them but a bank line. Each is avoidable with records kept as you go.
Records: What Makes a Write-Off Survive
The CRA can ask you to support any expense, and generally you need to keep records for six years from the end of the tax year they relate to. For a construction business that means job files, subcontractor invoices and T5018 records, WSIB documentation, equipment purchase records, and vehicle logbooks. Digital copies are acceptable provided they are complete and readable. Reconstructing this after a review begins costs far more than maintaining it, and is rarely as convincing.
Case Study: General Contractor, Ontario
A contractor came to us after several years of filing with a bookkeeper who had expensed every equipment purchase in the year of acquisition, left all materials and site costs in a single overhead account, claimed the owner's truck at 100% business use with no logbook, and never filed a T5018 despite paying a dozen subtrades every year. We reclassified the equipment into the correct capital cost allowance classes and restated the affected years, rebuilt the vehicle claim on a defensible business-use percentage, brought the T5018 filings current, and allocated materials and site costs to jobs. Two things came out of it. The deduction position was corrected before the CRA raised it rather than after, and the owner discovered that his highest-revenue job type had been his thinnest margin all along. The figures here are illustrative of the work we do, not a specific client file.
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