Your home office can generate significant tax savings — but eligibility rules are strict and you can never create a loss. Here's how to calculate your deduction correctly.
Know exactly what belongs on Line 9945 — and what the CRA says doesn't qualify.
Special CRA rules and percentage limits that apply to business-use-of-home expenses.
Your home workspace must meet ONE of two criteria: (1) it is your principal place of business, OR (2) it is used exclusively for business AND you regularly meet clients there.
Section 18(12) of the Income Tax ActHome office expenses cannot create or increase a business loss. If your home office expenses exceed your net business income, the unused amount carries forward to the next year.
Calculate your deduction as: workspace square feet / total home square feet. For shared rooms (not used exclusively for business), apply a time-based adjustment on top of the area percentage.
While technically allowed, claiming CCA on your principal residence can create a capital gains liability when you sell. Most tax advisors strongly recommend NOT claiming CCA on your home.
| Rule | Limit |
|---|---|
| Area-based calculation | Workspace sqft / Total home sqft |
| Time-based adjustment for shared rooms | Hours used for business / Total hours available |
See how different professionals use Line 9945 deductions in practice.
Used a dedicated 200 sq ft home office in an 1,800 sq ft home for full-time consulting work.
$18,000 total home costs × 11.1%
$2,000 (11.1%)
Used a 150 sq ft spare room in a 1,400 sq ft apartment exclusively for inventory storage and order fulfillment.
$16,800 total home costs × 10.7%
$1,798 (10.7%)
Converted a 250 sq ft basement area in a 2,000 sq ft home into a dedicated photography studio.
$20,000 total home costs × 12.5%
$2,500 (12.5%)
These errors on Line 9945 can trigger a CRA review — here's how to get it right.
Double-claiming utilities on both Line 9220 AND here
Home utilities (heat, electricity, water) go ONLY to Part 7 (Line 9945). Line 9220 is for dedicated business phone lines and the business portion of cellphone/internet. Never claim the same utility on both lines.
Not meeting eligibility criteria (principal place OR exclusive + regular client meetings)
Your workspace must be your principal place of business OR used exclusively for business and regularly for client meetings. A desk in your living room that you also use for personal activities may not qualify.
Creating a business loss with home office expenses (not allowed)
Home office expenses can reduce your business income to zero but cannot create a loss. Any excess carries forward to the next year. Plan your claims accordingly.
These categories are often mixed up with Business-Use-of-Home Expenses. Here's the difference.
Home utilities (heat, electricity, water) go HERE on Line 9945, not on Line 9220. Line 9220 is for dedicated business phone lines and cellphone/internet business-use portions.
Home rent goes HERE on Line 9945 as part of your business-use-of-home calculation. Line 8910 is for commercial space rent only (offices, studios, coworking).
Home property taxes go HERE on Line 9945 as part of your business-use-of-home calculation. Line 9180 is for property taxes on dedicated commercial property.
Home insurance goes HERE on Line 9945 as part of your business-use-of-home calculation. Line 8690 is for commercial business insurance only.
See how ScanForTax processes a typical home office expense.
Enbridge Gas
2025-01-20
Ontario
ScanForTax identifies this Enbridge gas bill and adds it to your business-use-of-home expenses (Line 9945). The deductible portion depends on your workspace percentage — for example, at 12% business use, $28.08 of the $235.04 would be deductible. The HST on the deductible portion is recoverable via ITC.
Profession-specific guides that frequently use Home Office deductions.
See how tax recovery works for home office expenses in each province.
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