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For informational purposes only. Not financial, legal, or professional advice. Consult a licensed mortgage professional before making decisions. See full disclaimer

FAQ Library
Refinance•Verified 2026-04-14

How do GDS and TDS ratios affect my refinancing options?

GDS (Gross Debt Service) and TDS (Total Debt Service) ratios are critical affordability indicators that financial institutions use to determine your eligibility for refinancing.

Key Points

  • When you refinance, lenders look at your income and debts conservatively, planning for different financial situations and potentially higher interest rates.

  • If your mortgage is insured, the lender must follow the insurer's rules about how much debt you can handle.

  • For uninsured mortgages, lenders will carefully assess your ability to repay, considering current and future financial conditions.

  • To qualify for refinancing without insurance, you'll generally need to qualify at your mortgage interest rate plus a buffer, or a set minimum qualifying rate, whichever is higher.

  • Lenders have specific guidelines on how your income and debts affect your ability to refinance, so ask them to explain their policies.

Need a Deeper Breakdown?

Read the full research guide this FAQ was derived from for more context and strategy.

Technical Research Verification

Our systems synchronized 3 data points and regulatory frameworks to verify this technical brief.

Read the deeper guide · Refinance

2026 Canadian Mortgage Refinance Guide: Costs & Break-Even Math

Related Questions

What is the Loan-to-Value (LTV) ratio, and how does it impact my ability to refinance?

The Loan-to-Value (LTV) ratio plays a critical role in the refinancing process.

How does OSFI's Guideline B-20 affect refinancing?

OSFI's Guideline B-20 establishes the benchmark for residential mortgage underwriting practices that federally regulated financial institutions (FRFIs) must adhere to.

What is a 'straight switch,' and how does it impact refinancing at renewal?

A "straight switch" refers to the process of transferring an existing uninsured mortgage to a new institution when it's up for renewal, without increasing the remaining amortization period or the loan amount.

What Loan-to-Value (LTV) Ratio is Right for Me?

The Loan-to-Value (LTV) ratio is a key metric lenders use to gauge risk.

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4.14%
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4.45%

GDS/TDS Formula

GDS = (Principal + Interest + Taxes + Heat + 50% Condo Fees) / Gross Income TDS = (PITH + Other Debts) / Gross Income

Calculation Breakdown: $500k Refinance Scenario

Consider a household with $100,000 gross annual income ($8,333/mo) refinancing into a $500,000 mortgage at 4.29% (5-year fixed) with a qualifying rate of 6.25% (stress test):

ComponentMonthly AmountNotes
Principal & Interest$3,232Based on 6.25% qualifying rate over 25 years
Property Taxes$333Estimated $4,000 annually
Heating Costs$100Standard estimate
Housing Total (PITH)$3,665Total core housing costs
Other Debts (Car, Credit)$500Assumed external obligations
Total Debt Load$4,165Total monthly obligations

Resulting Ratios:

  • GDS: 44.0% ($3,665 / $8,333) — Fail (Threshold ≤ 39%)
  • TDS: 50.0% ($4,165 / $8,333) — Fail (Threshold ≤ 44.0%)

In this scenario, both the housing costs (GDS) and total debt (TDS) exceed the allowable limits, requiring either a lower loan amount or debt reduction to qualify.