Business-Use-of-Home Expenses
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.
Business-use-of-home — the CRA's name for the home office deduction — lets self-employed Canadians deduct a share of their household costs on Line 9945 of the T2125. To qualify, your workspace must either be your principal place of business, or be used exclusively for business while regularly hosting client meetings. Meet one of those tests and a slice of your rent or mortgage interest, utilities, insurance, and property taxes becomes deductible.
The calculation is a simple proration: divide your workspace area by your home's total area. A 200 sq ft office in a 2,000 sq ft house is 10% — so 10% of eligible home costs are deductible. If the space isn't used exclusively for business (a kitchen-table setup, say), prorate again by hours of business use, and be ready to defend both numbers with a floor plan and a work schedule.
Renters have it simplest: the business percentage of rent is deductible. Homeowners deduct the same percentage of mortgage interest (never the principal), property taxes, and home insurance. Utilities — heat, electricity, water — follow the same split, while the business portion of internet and phone is claimed separately on Line 9220. Keep every bill: these are exactly the receipts that pile up across a year.
Two rules keep this deduction honest. First, home office expenses cannot create or increase a business loss — anything you can't use this year carries forward indefinitely to future years. Second, resist claiming capital cost allowance on the home itself: it converts part of your tax-free principal residence into a taxable asset when you sell.
What You Can (and Can't) Deduct
Know exactly what belongs on Line 9945 — and what the CRA says doesn't qualify.
What Qualifies
- Heat (gas, oil, electricity)
- Electricity
- Home insurance
- Mortgage interest (NOT principal)
- Property taxes
- Rent
- Maintenance and cleaning
- Minor repairs
- Water
- Internet (business portion)
Does NOT Qualify
- Mortgage principal
- Personal expenses
- Major renovations (CCA instead)
- Expenses exceeding net business income
Rules & Limits
Special CRA rules and percentage limits that apply to business-use-of-home expenses.
Special Rules
Eligibility Requirements
Heads upYour 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 ActCannot Create or Increase a Business Loss
Heads upHome 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.
Area-Based Calculation
AdvantageCalculate 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.
Do NOT Claim CCA on Your Home
Heads upWhile 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.
Percentage Limits
| Rule | Limit |
|---|---|
| Area-based calculation | Workspace sqft / Total home sqft |
| Time-based adjustment for shared rooms | Hours used for business / Total hours available |
Real-World Examples
See how different professionals use Line 9945 deductions in practice.
Dedicated Home Office (11.1% of Home)
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%)
Spare Room for Inventory/Shipping (10.7%)
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%)
Home Photography Studio (12.5%)
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%)
Common Mistakes to Avoid
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.
Commonly Confused Categories
These categories are often mixed up with Business-Use-of-Home Expenses. Here's the difference.
Telephone & Utilities
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.
Rent
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).
Property Taxes
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.
Insurance
Home insurance goes HERE on Line 9945 as part of your business-use-of-home calculation. Line 8690 is for commercial business insurance only.
Sample Receipt Walkthrough
See how ScanForTax processes a typical home office expense.
Enbridge Gas
2025-01-20
Ontario
How ScanForTax categorizes this
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.
Tax Calculation Breakdown
See the exact tax math for a typical home office purchase.
$235.04 Monthly Gas Bill (12% business-use home office)
Ontario
At a 12% business-use percentage, about $28.20 of this $235.04 bill lands on Line 9945. If you are GST/HST-registered, only the HST on the business portion (≈$3.24) is recoverable as an ITC — the remaining 88% of the bill is a personal expense.
Frequently Asked Questions
Do I qualify for the home office deduction?
How do I calculate the deduction?
Should I claim CCA on my home?
Can home office expenses create a business loss?
Can I claim my mortgage payment for a home office?
What percentage of my home can I claim?
Related Professions
Profession-specific guides that frequently use Home Office deductions.
Tax Guides by Province
See how tax recovery works for home office expenses in each province.
Related Expense Categories
Tax deadline is April 30th.
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