Finally! Here is a comprehensive explanation as to why people may get different credit scores when they run their credit than when the mortgage company does.

From the Wall Street Journal Article, “A Battle Plan for Refinancing Your Mortgage” published 5/20/09:

Your credit score. Whether you get today's lowest rates will depend next on your credit score, a measure of how big a credit risk you may be. Borrowers who want the best rates generally need a FICO score -- based on a formula developed by Fair Isaac Corp. -- of 740 or above out of a possible 850. Those with FICO scores between 620 and 740 will pay either higher interest rates or more upfront "points" or fees, and those with scores below 620 may not be able to land a loan at all.

That seems simple enough until you realize that the nation's three main credit bureaus -- TransUnion, Experian and Equifax -- all calculate their FICO scores differently. So lenders typically pull all three scores and take the middle one, or a couple's lowest middle score.

Getting your number. Finding your actual scores is a bit like trying to read tarot cards. The Web site Credit Karma (www.creditkarma.com) offers a free credit score, but it's the TransUnion TransRisk score, not your FICO score. Experian (www.experian.com) sells consumers its Experian Plus scores but doesn't make its FICO score available directly to the public.

You can buy TransUnion and Equifax FICO scores from MyFico.com, but they may not be the same scores your lender sees. That's because you actually have multiple FICO scores, with different equations for auto loans, credit cards and mortgages.

All those scores, however, should be fairly consistent, giving you a good idea of whether your credit is good or great. If your scores are lower than you'd expect or if they vary widely, check your credit reports for errors. You can retrieve all three credit reports free of charge once a year at AnnualCreditReport.com.