It was never about what secured the loan

The advice she'd been given was confident and wrong: the interest can't be deductible because the loan is registered against your house, not your business. On that understanding she'd nearly gone looking for a far more expensive unsecured business line of credit instead of refinancing a mortgage she already qualified for.

Security has nothing to do with it. The Canada Revenue Agency's own position, set out in Income Tax Folio S3-F6-C1, is built entirely around a different question.

The real obstacle was never approval. It was making sure that, years from now, every dollar of the $150,000 could still be traced to the business rather than absorbed into her household's general cash flow — which required a specific structure at closing, not just a stated intention.

This is a conventional refinance to 75% loan-to-value, so the ratios were sized against the lender's own policy rather than an insurer's ceiling — one of the practical differences covered in insured vs. uninsured underwriting — and cleared comfortably.

Both ratios cleared with room; the deductibility question sat entirely on the other side of closing, in how the $150,000 was actually disbursed and spent from there.

A mortgage agent licensed under Ontario's Mortgage Brokerages, Lenders and Administrators Act treated the refinance and the tax structuring as two connected but separate jobs.

First, corrected the security misconception directly, walking through Folio S3-F6-C1's own framing: what secures a loan is irrelevant to paragraph 20(1)(c); what the borrowed money is used for is everything.

Second, had the payout instructions route the full $150,000 as a single lump sum into a newly opened business account used for nothing else — not blended into a readvanceable line of credit, not netted against the existing mortgage, and not deposited into her existing business operating account where it would mix with regular sales revenue.

Third, coordinated with her accountant on what CRA calls ‘cash damming’ — segregating the borrowed funds so every dollar leaving that account for inventory or the renovation stays traceable to the loan, while ordinary business revenue continues through her existing account untouched. The same discipline is worth applying wherever a self-employed income worksheet mixes business and personal cash flow.

The refinance funded at $360,000, 75% loan-to-value, on a five-year fixed at 5.49%, qualifying payment $2,631, GDS 35.8% and TDS 39.8%. The full $150,000 landed in a single, segregated business account opened the same week, with nothing else ever deposited into it.

This is a conventional (uninsured) refinance, so CMHC's ratio ceilings do not bind directly; 39%/44% are shown as the lender's own applied policy, not an insurer's rule.

• 01Interest deductibility turns on the use of borrowed money, not what secures it. A mortgage against a principal residence can fund fully deductible business interest, provided the proceeds genuinely go toward earning income.
• 02Tracing beats intention. CRA's own folio is built around whether borrowed money can be traced to its income-earning use — commingling it with other funds is what defeats a deduction, not the client's stated purpose.
• 03‘Cash damming’ is a real, named technique, not an invented workaround. Segregating borrowed funds into their own account, apart from every other dollar, is exactly what CRA's Income Tax Folio S3-F6-C1 describes as the way to keep a use traceable.
• 04Get the disbursement structure right at closing. A blended readvanceable facility or a deposit into an existing operating account can undo a deduction that a clean, segregated lump sum would have protected.