Fannie Mae has narrowed the circumstances under which home lenders must reunderwrite applications submitted by borrowers who take on other debts before the mortgage closes.

Lenders now have to resubmit a loan to Fannie's Desktop Underwriting system if a borrower's recalculated debt-to-income ratio exceeds 45%, or if the ratio rises by 3 percentage points or more, the government-sponsored enterprise said Friday.

Previously, a loan had to be reunderwritten if the undisclosed debts caused the debt-to-income ratio to rise by more than 2 percentage points.

Since June, Fannie has required lenders to check for any undisclosed liabilities a borrower has taken on after applying for the mortgage. The GSE reiterated Friday that this does not necessarily mean lenders must pull a second credit report before closing, though some lenders have said they are doing so.

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