Debt Service Ratio

A debt service ratio is a measurement comparing the debt payments you carry against your gross income, and it is one of the main tests Canadian lenders use when deciding whether you qualify for a mortgage. Instead of looking at income on its own, a lender checks whether the payments attached to the property, plus your other debts, fit inside a limit the lender sets.

Two ratios, one idea

Mortgage qualification in Canada normally uses two versions of the same idea. The Gross Debt Service Ratio (GDS) looks at housing costs only. The Total Debt Service Ratio (TDS) starts with those housing costs and adds every other required debt payment.

Payment counted	GDS	TDS
Mortgage principal and interest, or rent	Yes	Yes
Property taxes and heating	Yes	Yes
Half of condo or strata fees, where applicable	Yes	Yes
Credit cards, car loans, lines of credit, student loans	No	Yes
Support payments and other required obligations	No	Yes

Both are expressed as a percentage of gross annual income, meaning income before deductions. Lenders compare the result to a cap they set, guided by CMHC-insured lending rules and OSFI's residential mortgage underwriting expectations under Guideline B-20.

The stress test sits on top

Before the ratios are applied, the federal mortgage stress test requires that your payments be checked at a qualifying rate higher than the rate you would actually pay. The mortgage payment used in the GDS and TDS calculation can therefore be larger than the one on your contract, which raises both ratios and reduces how much you can borrow. See the mortgage stress test for how the qualifying rate is set.

Why it matters to you

These ratios explain why two households with the same income can qualify for very different mortgage amounts. A large car payment or a stack of credit card balances pushes TDS up and shrinks the mortgage a lender is willing to approve. Borrowers commonly change the outcome by paying down or consolidating debts, increasing the down payment, choosing a longer amortization to lower the payment, or applying with a co-signer. The GDS and TDS guide walks through how lenders measure affordability.

The result is an estimate of capacity, not a promise of approval. Lenders also weigh credit history, income verification, and the source of your down payment, and self-employed applicants or rental property owners using rental offset may be assessed differently.

Frequently asked questions

What is a good debt service ratio in Canada?

Canadian lenders generally look for a GDS ratio comfortably under their stated cap and a TDS ratio below a slightly higher cap, with the exact limits set by the lender and influenced by CMHC-insured lending rules and OSFI underwriting guidance. A lower ratio leaves more room in a budget and can strengthen an application, but it does not guarantee approval on its own.

Is debt service ratio the same as debt-to-income ratio?

They are related but not identical. Debt-to-income compares total debt balances with income, while the debt service ratios used in Canadian mortgage qualification focus on the actual payments: principal, interest, property taxes and heating for the housing side, plus other required debt payments, all measured against gross annual income.

How can I lower my debt service ratio before applying?

Paying down or consolidating credit card balances, car loans and lines of credit reduces the payments counted in TDS. Increasing your down payment, lengthening the amortization to lower the required payment, or applying with a co-signer whose income and debts are included can also shift the calculation. Confirm the details with your lender before relying on an estimate.