How a Line of Credit Affects a Canadian Mortgage Application

Lenders count the full limit of a revolving line of credit when they calculate your debt ratios — not the balance. An unused line with a zero balance can still reduce the mortgage you qualify for, because the lender has to assume you could draw on it at any time. The practical response is to reduce or close limits before you apply, and to find out in advance how your lender treats unused credit, because the treatment varies from one institution to the next.

Why a limit counts even at a zero balance

Underwriting is forward-looking. The lender is not measuring what you owe today; it is measuring what you could owe after closing. A revolving facility can be drawn without further approval, so an unused limit is treated as debt that could appear on your next statement.

OSFI's Guideline B-20 sets the residential mortgage underwriting expectations that federally regulated lenders follow, including how a borrower's capacity to carry debt is assessed. It does not tell lenders to ignore unused credit — it requires them to assess the whole picture, which in practice means the limit.

The two ratios that decide the file

Gross debt service (GDS) covers housing costs — the mortgage payment, property taxes, heat, and half of condo fees where they apply — divided by gross income. Total debt service (TDS) adds every other debt payment: car loans, credit cards, student loans, personal lines of credit, support obligations.

Federally regulated mortgage lenders generally work to a TDS ceiling of about 44%. Under Guideline B-20 they also qualify the borrower at a stress-test rate above the contract rate, so the ratio is tested against a larger mortgage payment than the one you will start out paying.

That combination is what catches people. The assumed payment on a large unused limit goes into the numerator of TDS, and the stress test inflates the mortgage payment in that same numerator. Two pressures, one ratio — driven by a limit you never intended to use.

How each kind of debt is counted

The table below shows the common treatment. Approaches vary by lender, so the only way to know your own lender's version is to ask and get the answer in writing.

The assumed payment on unused limits

A line of credit has no fixed amortisation, so there is no scheduled payment to read off a statement. Lenders substitute an assumed payment, calculated as a percentage of the limit or of the balance using a factor set by that lender's own policy. A larger limit produces a larger assumed payment; a larger assumed payment raises TDS and shrinks the mortgage you can carry.

This is the core of it: a zero balance and a zero limit are not the same thing to an underwriter. Reducing the limit — not just the balance — is what changes the arithmetic.

Secured lines of credit and the home equity ceiling

If your line of credit is a home equity line of credit, the limit is constrained by regulation as well as by income. At federally regulated lenders, home equity lines of credit are generally limited to 65% of appraised property value, with total secured lending against the property usually capped at 80%.

That cuts two ways. Existing secured debt consumes room you might otherwise use for a refinance or a purchase. And a HELOC is often registered as a collateral charge, which many lenders treat differently from a standard charge when you want to move the mortgage to another lender at renewal.

Line of credit meaning: the terms that decide the cost

People search for “line of credit loan”, but a line of credit and a loan are different products, and the difference explains the pricing:

• Revolving versus instalment. A line of credit revolves — draw, repay, draw again, limit unchanged. A loan is instalment credit: advanced once, repaid on a schedule.
• Secured versus unsecured. A HELOC is secured by your home; an unsecured line rests on your creditworthiness alone. Secured borrowing usually prices lower because the lender's risk is lower.
• Demand facility. Most lines of credit are repayable on demand. The lender can reduce the limit or require repayment, which is a genuine risk if your income or circumstances change.
• Variable pricing. Lines of credit are typically priced off a benchmark and move with it. Canadian fixed-rate mortgages are compounded semi-annually by law, but that convention does not apply to most revolving credit.
• Readvanceable. Some secured lines increase automatically as you pay down the mortgage, which grows the limit — and therefore grows what the next lender counts against you.

What to do before you apply

1. Pull both credit reports. Canada has two national bureaus — Equifax Canada and TransUnion Canada — and a free copy of your report is available from each. Check that every limit is reported correctly; an inflated limit that is not yours still skews the ratio.
2. List every revolving limit. Cards, unsecured lines, HELOC, overdraft, and any buy-now-pay-later facility that reports. Add the limits up and look at the total honestly.
3. Ask how your lender counts them. Specifically: is an unused limit included, and what assumed payment factor applies? Two lenders can reach different answers on the same file.
4. Reduce before you close. Lowering a limit cuts the assumed payment. Closing an older card can shorten your credit history and change your utilization, so weigh both effects before cancelling anything.
5. Open nothing new. A new limit added between pre-approval and funding can push TDS past the ceiling, and lenders can re-run the file before advancing funds.
6. Plan for a borrowed down payment. If any part of your down payment is drawn from a line of credit, the lender counts both the new debt and the source. Model it before submission, not after.
7. Re-run the numbers after any change. Closing a limit alters the arithmetic, so ask for the calculation to be redone rather than assuming it improved.

Where borrowers get caught

• Treating a pre-approval as a commitment. It is usually based on information you supplied. Final approval comes after the full file is verified, including your debts as they stand on that day.
• Drawing on a line for the down payment without modelling it. The draw raises your debt and the assumed payment, and it can weaken the equity position the lender is looking at.
• Assuming an unused limit is invisible. It is not. A large unused limit that was never reduced is one of the most common reasons a file that “should” work does not.

If your ratios are already over the ceiling

The options are narrow but real: pay down or close revolving limits, let accounts age, add a co-borrower, or lower the purchase price. A licensed mortgage professional can model the file at the stress-test rate before you submit it. The Financial Consumer Agency of Canada also publishes plain-language material on mortgages, renewals and affordability.

If the obstacle is unmanageable debt rather than a mortgage, a non-profit credit counselling service can help you plan. Note that only a licensed insolvency trustee can administer a consumer proposal or a bankruptcy, and trustees are regulated by the Office of the Superintendent of Bankruptcy Canada. Timing matters: a consumer proposal stays on a credit report for three years after completion or six years from filing, whichever comes first, and a first bankruptcy stays on the report for six years after discharge.

If you have a complaint about how an account or limit was handled, consumer complaints involving federally regulated financial institutions are handled by the Financial Consumer Agency of Canada, while provinces license and supervise most other lenders and each maintains a consumer protection office.

Significant borrowing decisions depend on your individual circumstances, and regulated professional advice — from a licensed mortgage professional, an accountant, or a licensed insolvency trustee — is appropriate before you commit.

Loanwolf.ca is a matching service, not a lender. We do not make loans, set rates, or make credit decisions; we connect Canadians with lenders and brokers who may be able to help. The lowest rates go to the most qualified applicants: strong credit, verifiable income, and debt ratios comfortably inside the lender's ceiling. Reducing an unused limit before you apply is often the difference between being offered a rate and being declined for one.