Your home office deduction is the business-use share of your eligible home costs. Divide your workspace area by your home's total finished area, multiply by your eligible expenses (utilities, insurance, maintenance, and rent for renters; owners add mortgage interest and property tax), and — if the room is also used personally — prorate by hours ÷ 24. It's claimed on Form T2125, Part 7, and it can never create or increase a business loss; any excess carries forward.
Use the same unit for both (sq ft or sq m). Your workspace is 12.5% of your home by area.
You can deduct this year
$3,163
12.5% business use of $25,300 in eligible costs.
On Form T2125 this is Part 7, claimed on line 9945. Owners deduct mortgage interest only — never principal — plus property tax; renters deduct a share of rent. Utilities, insurance, and maintenance apply to both.
Estimate only, using the CRA detailed method (the temporary flat-rate method has ended). It doesn't model capital cost allowance (claiming CCA on your home can trigger capital-gains tax when you sell), GST/HST input credits, or your full return. Not tax advice — see the Sources below and confirm with a Canadian accountant.
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A worked example
Say you rent, and you have a dedicated 150 sq ft office in a 1,200 sq ft apartment — that's 12.5% business use. Your eligible annual costs are $2,400 utilities, $700 insurance, $600 maintenance, and $21,600 rent — $25,300 in total.
So this year you deduct $3,163. Because your $55,000 of net income easily covers it, there's no cap and nothing to carry forward. But flip the income to, say, $2,000 and the rule bites: you could only claim $2,000 this year, and the remaining $1,163 would carry forward to a future year. That net-income cap — home-office expenses can't create or increase a loss — is the detail most quick calculators get wrong.
Sources
Every rule in this calculator is drawn directly from the CRA, verified against the live pages below:
- CRA — Business-use-of-home expenses (T2125)
Area-basis proration, hours ÷ 24 for shared space, eligible expenses (utilities, insurance, maintenance, property tax, mortgage interest), rent for renters, the net-income cap, and the carryforward.
- CRA — Guide T4002, Self-employed Business, Professional, Commission, Farming, and Fishing Income
The full guide behind Form T2125, including business-use-of-home expenses and Part 7.
- CRA — Income Tax Folio S4-F2-C2, Business Use of Home Expenses
The detailed technical interpretation of the deduction rules.
Keep going
Your home office is one deduction — the next question is how much tax to set aside on what's left. Use the tax set-aside calculator to size your monthly CRA jar, read the CRA tax filing guide for the self-employed to see where line 9945 sits on Form T2125, and start from the complete guide to self-employed taxes in Canada for the whole map.
People also ask
How much of my home office can I deduct if I am self-employed in Canada?
You deduct the business-use share of your eligible home costs. Take the area of your workspace divided by the total finished area of your home — for example a 150 sq ft office in a 1,200 sq ft home is 12.5%. Multiply that percentage by your eligible expenses (utilities, home insurance, maintenance, and rent if you rent; owners add mortgage interest and property tax). If the space is also used for personal living, you prorate by hours too: hours used for business ÷ 24. The calculator above does the full math.
What home office expenses can a self-employed person deduct in Canada?
Under the CRA detailed method you can deduct a prorated share of heating and utilities, home or tenant insurance, and maintenance and repairs. Renters add a share of rent. Homeowners add mortgage interest — interest only, never the principal — and property tax. You claim it on Form T2125, Part 7, line 9945. Note: claiming capital cost allowance (CCA / depreciation) on your home is possible but usually a bad idea, because it makes part of any future sale taxable, so most sole proprietors leave it out.
Can a home office deduction create a business loss?
No. This is the rule most simple calculators miss: your business-use-of-home expenses cannot be more than your net business income before those expenses — they cannot create or increase a loss. If your eligible deduction is larger than your net income, you claim only up to your income this year and the rest carries forward to a future year, when your income can absorb it. The calculator flags the cap and shows your carryforward.
Can I deduct home office expenses if I rent?
Yes. Renters deduct the business-use share of rent, plus the same share of utilities, insurance, and maintenance. In many cases renters end up with a larger deduction than owners on a similar space, because rent is fully eligible for proration while owners can only use the interest portion of a mortgage payment, not the principal.
Do homeowners deduct their whole mortgage payment?
No — only the interest portion. Mortgage principal is never deductible (it is building equity, not an expense), so owners include mortgage interest and property tax alongside utilities, insurance, and maintenance. Everything is then multiplied by your business-use percentage.
Is the temporary flat-rate home office method still available?
No. The temporary flat-rate method (the $2-per-day shortcut from the pandemic years) has ended. Self-employed Canadians use the detailed method — the area-and-expenses calculation this tool performs — and complete Part 7 of Form T2125.
Every deduction, ready in April.
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