Mortgage Guaranty Insurance Corp., the nation's leading private mortgage insurer, is loosening its underwriting guidelines in a series of changes effective either Dec. 1, 2010 or Jan. 1, 2011. The company said it regularly changes its guidelines to accommodate and reflect current market conditions. Starting Dec. 1, MGIC will insure mortgages with a debt-to-income ratio up to 45% if the borrower has a credit score equal to or greater then 740. The loan must also be either a fixed-rate product or minimum 5-year adjustable-rate. MGIC will also consider underwriting loans for "flipped" properties — a property acquired by a seller less than 90 days before the purchase contract. However, the firm said a full-file MGIC underwrite is required on any property acquired by a seller less than 180 days before the purchase contract closing date. The minimum credit score for Tier Two jumbo loans (more than $417,000) will be 720 as of Dec. 1, down from 760.