GDS and TDS Ratios

GDS stands for Gross Debt Service, and it measures the share of a borrower's gross monthly income needed to cover core housing costs. In BC, lenders following CMHC's underwriting standards calculate GDS using the PITH formula: mortgage principal and interest, property taxes, home heating costs, and 50% of applicable strata fees where the property is a strata lot under the Strata Property Act (SBC 1998, c. 43). This ratio helps lenders determine whether a borrower can afford the carrying costs of the specific property being purchased.

GDS covers only the housing-related costs described in the PITH formula, while TDS (Total Debt Service) adds all other monthly debt obligations — such as car loans, credit card minimum payments, student loans, and lines of credit — to that housing figure. Both ratios are then expressed as a percentage of the borrower's gross monthly income, giving the lender a fuller picture of overall debt load. Because TDS is always equal to or greater than GDS, a borrower can pass the GDS test but still be declined if their non-housing debts push TDS above the lender's threshold.

For mortgages requiring CMHC default insurance — generally those with a down payment of less than 20% — CMHC's current underwriting standards cap GDS at 39% and TDS at 44% of gross income, with limited exceptions available to borrowers with strong credit profiles. These thresholds apply across Canada, including BC, and are set by CMHC as the national default insurer. Borrowers who exceed these caps will generally need to reduce the purchase price, increase their down payment, or pay down other debts before qualifying.

Yes — when a BC property is a strata lot governed by the Strata Property Act (SBC 1998, c. 43), lenders following CMHC's PITH formula include 50% of the monthly strata fee in the GDS calculation. This means that higher strata fees directly reduce the maximum mortgage amount a borrower can qualify for, because more of their gross income is deemed consumed by housing costs. Buyers of strata properties in BC should therefore factor strata fees into their affordability planning before making an offer.

Under OSFI Guideline B-20, federally regulated lenders in BC must qualify uninsured mortgage applicants at the higher of the contract interest rate plus 2%, or a prescribed floor rate set by OSFI. The stress test does not replace GDS and TDS analysis — instead, the lender applies the GDS and TDS ratio caps using the stressed (higher) qualifying rate rather than the actual contract rate, which reduces the maximum loan amount the borrower qualifies for. For insured mortgages, CMHC applies the same stress-test principle in conjunction with its 39% GDS and 44% TDS caps.

CMHC's underwriting guidelines do permit limited exceptions to the 39% GDS and 44% TDS caps for borrowers who demonstrate strong compensating factors, most notably a high credit score. However, these exceptions are at the insurer's discretion, are not guaranteed, and are applied narrowly. Borrowers in BC who anticipate being near or above these thresholds should discuss their specific financial profile with a licensed mortgage professional.

Under the Real Estate Services Act (RESA) and BCFSA's requirements, a BC real estate licensee has a duty to act in the best interests of their client and to provide information material to the transaction. While mortgage qualification calculations like GDS and TDS are primarily within the domain of lenders and mortgage brokers, a licensee is expected to ensure clients understand the importance of obtaining financing pre-approval before making an offer. A licensee who misrepresents a client's financing ability or conceals material affordability concerns may be subject to regulatory action by the BCFSA.

Because 50% of monthly strata fees are included in the GDS numerator under CMHC's PITH formula, a strata property with high monthly fees effectively leaves less gross income available to service principal and interest, reducing the maximum mortgage amount the lender will approve. For example, a strata lot in a BC building with significant amenities — and therefore higher fees — may qualify a buyer for a meaningfully smaller loan than a freehold property at the same price point. Buyers governed by the Strata Property Act (SBC 1998, c. 43) should confirm the current strata fees, including any special levies, before completing their mortgage pre-approval.

Conventional lenders — those offering uninsured mortgages to borrowers with 20% or more down payment — are not legally required to use the exact same CMHC thresholds, but federally regulated lenders must comply with OSFI Guideline B-20, which directs them to establish and apply sound debt-service ratio policies. In practice, many BC lenders apply GDS and TDS thresholds similar to CMHC's 39%/44% caps, though some lenders exercise discretion and may apply different limits. Credit unions in BC are provincially regulated and are not directly bound by OSFI Guideline B-20, but they establish their own underwriting standards that typically include analogous debt-service ratio tests.

When two or more borrowers apply jointly for a mortgage in BC, lenders generally combine the gross incomes of all borrowers to form the denominator of the GDS and TDS ratios, and combine all qualifying housing costs and debt obligations as the numerator. This means a co-borrower's income can increase the maximum qualifying mortgage, but their existing debts — such as car loans or credit card minimums — will also increase the TDS numerator and can offset that benefit. Lenders and mortgage insurers evaluate the combined financial profile against the applicable GDS and TDS thresholds.