Canada: GDS and TDS, and what goes into them
Canada runs two ratios with names of their own, and the difference between them is what most calculators get wrong. Gross debt service covers housing alone and is capped at 39% of gross income. Total debt service adds every other debt payment and is capped at 44%. CMHC will not insure a mortgage above the TDS limit, so for a default-insured loan these are hard numbers rather than guidance; uninsured lending can be slightly more generous.
What counts as housing is more than the mortgage. GDS includes the payment, property tax, heat, and half of any condominium fees. Heating costs are a real line in a Canadian application, and the half-of-condo-fees convention means a $600 monthly fee adds $300 to the ratio, not $600. Leaving those out is the single most common way a Canadian ratio comes out flattering and then fails at the lender.
Income is assessed before tax, and the ratios are only half the assessment. Insured borrowers must also clear the mortgage stress test at a qualifying rate above the contract rate, so a file can sit inside 39/44 and still be declined on the stressed payment.
GDS at 39% allows $3,510 of housing including tax, heat and half the condo fee. TDS at 44% allows $3,960 for everything. A $450 car payment therefore consumes the entire gap between the two ratios, and the housing figure has to fall to fit.