# How does OSFI's Guideline B-20 affect mortgage underwriting?

> OSFI's Guideline B-20 sets the standards for prudent residential mortgage underwriting, applicable to all federally regulated financial institutions (FRFIs).

Category: Renewal
Last verified: 2026-02-18
Source: https://ratellow.com/faqs/renewal/how-does-osfis-guideline-b-20-affect-mortgage-underwriting

## Answer
OSFI's Guideline B-20 sets the standards for prudent residential mortgage underwriting, applicable to all federally regulated financial institutions (FRFIs). It emphasizes assessing a borrower's willingness and capacity to service their debt obligations. Understanding the five fundamental principles in B-20 is critical for sound mortgage practices and risk management.

## Institutional highlights
- Your lender must have a solid plan for managing mortgage risk.
- Lenders should look at your whole financial picture when deciding if you qualify.
- Good lending practices help keep the mortgage system stable for everyone.
- Your lender can't rely on mortgage insurance to make up for poor lending decisions.
- Clear information from lenders helps you understand your mortgage and builds trust.

## Related guide
- https://ratellow.com/guides/renewal-lump-sum-max

## Sources
- OSFI exempts uninsured mortgage straight switches from the prescribed MQR and implements portfolio LTI limits — https://www.osfi-bsif.gc.ca/en/guidance/guidance-library/osfi-exempts-uninsured-mortgage-straight-switches-prescribed-mqr-implements-portfolio-lti-limits
- Disclosure requirements — https://www.osfi-bsif.gc.ca/en/guidance/guidance-library/residential-mortgage-underwriting-practices-procedures-guideline-2017#3.1
- I. Purpose and scope of the guideline — https://www.osfi-bsif.gc.ca/en/guidance/guidance-library/residential-mortgage-underwriting-practices-procedures-guideline-2017#1.0