Definition
The TDSR (Total Debt Service Ratio) is one of two fundamental mortgage qualification ratios. It measures the share of your gross monthly income that goes to paying all debts — mortgage included.
Formula: TDSR = (mortgage payment + property taxes + heating + 50% of condo fees + minimum card payments + car payments + other loans + alimony paid) ÷ gross monthly income × 100.
Standard cap: 44% at most OSFI-regulated A lenders. B lenders go up to 50-55% in exchange for a higher rate. The calculation is performed on the stressed qualifying rate (stress test) for B-20 mortgages, not the actual contractual rate. A TDSR of 39-42% is considered healthy; above 44%, the file needs compensating factors (higher down payment, 760+ score, guarantor).