Why Lenders Audit DTI Ratios
In mortgage underwriting, your credit score evaluates your repayment reliability, but your Debt-to-Income (DTI) ratio evaluates your monthly budget capacity. The DTI ratio is the primary indicator of whether an unexpected financial challenge or emergency might cause a mortgage default.
For qualified mortgages (QMs) in the United States, back-end DTI is generally capped at 43%. While some lenders offer exemptions up to 50% for borrowers with excellent credit scores or significant cash reserves, staying under 36% helps secure the lowest loan interest rates.
Front-End vs. Back-End Math
The calculations use gross income before standard deductions: