GDS and TDS Ratios

GDS stands for Gross Debt Service ratio, and TDS stands for Total Debt Service ratio. These are the two debt-service ratios that federally regulated lenders and most conventional lenders in BC use to assess whether a borrower can afford a mortgage. Canada Mortgage and Housing Corporation (CMHC) and lenders operating under the Office of the Superintendent of Financial Institutions (OSFI) Guideline B-20 apply these ratios to determine the maximum loan amount a borrower qualifies for. Verify current lender-specific policies with a BC mortgage broker or financial institution before applying.

The GDS ratio is calculated by dividing the borrower's monthly housing costs by gross monthly income, expressed as a percentage. Housing costs typically include mortgage principal and interest, property taxes, heating, and 50% of strata fees (as of 2026-07-27 — verify current) where applicable, following CMHC's PITH formula. For example, if monthly housing costs are $2,000 and gross monthly income is $6,000, the GDS ratio is approximately 33% (as of 2026-07-27 — verify current). Verify the exact formula and any lender-specific variations with a BC mortgage broker or lender.

For mortgages requiring default insurance (high-ratio mortgages with less than 20% down payment as of 2026-07-27 — verify current), CMHC's standard underwriting guideline generally caps the GDS ratio at 39% (as of 2026-07-27 — verify current). Limited exceptions may apply for borrowers with strong credit profiles or other compensating factors. CMHC is a federal Crown corporation and sets these thresholds nationally; verify current underwriting limits directly with CMHC or your lender before making purchase decisions. Conventional (uninsured) lenders in BC may apply different thresholds under OSFI Guideline B-20.

The TDS (Total Debt Service) ratio includes all the same housing costs as GDS, plus all other monthly debt obligations such as car loans, credit-card minimum payments, student loans, lines of credit, and other recurring debts. TDS is calculated by dividing total monthly housing costs plus other debts by gross monthly income. CMHC's current standard cap for insured mortgages is 44% TDS (as of 2026-07-27 — verify current), meaning no more than 44% of gross income should service housing and all other debt combined. Verify current lender requirements with a BC mortgage broker or financial institution.

Yes. For insured (high-ratio) mortgages, CMHC and other mortgage default insurers set maximum GDS (39% as of 2026-07-27 — verify current) and TDS (44% as of 2026-07-27 — verify current) thresholds as underwriting standards. For conventional (uninsured) mortgages with 20% or more down payment (as of 2026-07-27 — verify current), federally regulated lenders apply similar debt-service ratio limits at their discretion under OSFI Guideline B-20. Verify your lender's specific underwriting criteria with a BC mortgage broker or directly with the financial institution before applying.

Yes. Under CMHC's PITH formula (principal, interest, property taxes, heating), strata fees (also called strata maintenance fees) are included, typically at 50% of the monthly amount (as of 2026-07-27 — verify current). The Strata Property Act, SBC 1998, c. 43, governs strata corporations and strata fees in BC, but the inclusion of strata fees in GDS calculations is a lender underwriting practice set by CMHC and individual financial institutions. Verify how your lender treats strata fees in debt-service ratio calculations with a BC mortgage broker or lender before making an offer.

A higher GDS or TDS ratio generally means the maximum mortgage amount a lender will approve is reduced, or you may not qualify for the requested loan amount. Borrowers exceeding CMHC's 39% GDS or 44% TDS thresholds (as of 2026-07-27 — verify current) for insured mortgages typically must make a larger down payment (20% or more as of 2026-07-27 — verify current) to access conventional financing, which may allow slightly more flexibility. Some lenders may also require compensating factors such as higher credit scores, liquid reserves, or guarantors. Verify qualification options and alternatives with a BC mortgage broker, as policies vary by lender and are subject to OSFI Guideline B-20.

No. GDS and TDS ratio limits are set by federally regulated mortgage insurers (CMHC, Sagen, Canada Guaranty) and by individual lenders under the supervision of the Office of the Superintendent of Financial Institutions (OSFI) through Guideline B-20, which is federal in scope. BC does not have provincial legislation mandating specific debt-service ratios for residential mortgages. The British Columbia Financial Services Authority (BCFSA) regulates mortgage brokers under the Real Estate Services Act (RESA), SBC 2004, c. 42, but does not set debt-service ratio caps. Verify underwriting criteria directly with your lender or a BC licensed mortgage broker.

Under OSFI Guideline B-20, federally regulated lenders in BC must qualify uninsured mortgage borrowers at the higher of the contract mortgage rate plus 2% (as of 2026-07-27 — verify current) or a minimum qualifying rate set by the Bank of Canada (5.25% as of 2026-07-27 — verify current). GDS and TDS ratios are calculated using this higher qualifying rate, not the actual contract rate, which typically reduces the maximum mortgage amount for which a borrower qualifies. Insured mortgages are subject to similar stress-test requirements under CMHC and other insurers' underwriting rules. Verify current stress-test rates and their impact on your debt-service ratios with a BC mortgage broker or lender before making an offer.

The Financial Consumer Agency of Canada (FCAC), a federal agency, provides online mortgage affordability calculators and educational resources at www.canada.ca that include GDS and TDS estimates. CMHC also publishes underwriting guidelines and affordability tools at www.cmhc-schl.gc.ca. For a detailed pre-qualification based on your specific financial situation and current lender criteria, consult a BC licensed mortgage broker regulated under the Real Estate Services Act (RESA), SBC 2004, c. 42, and supervised by the British Columbia Financial Services Authority (BCFSA). Always verify current debt-service ratio thresholds and lender policies before making a purchase offer, as rules and rates change.