The FICO score your lender pulls for your mortgage application may not be the same as the FICO score your credit card company might be sending you every month online. (iStock)

When is your “credit score” irrelevant in buying a house or refinancing a mortgage? A new federal legal settlement with a major credit bureau has the answer: The only score that matters is the one your lender uses to evaluate you, not some random score you got on a website.

All the others you might buy or see — there are dozens of them hawked on the Internet — may be interesting, but they won’t affect the interest rates you’re quoted, the fees you’re charged or whether your application gets approved or rejected.

The new legal settlement from the Consumer Financial Protection Bureau alleges that Experian, one of the big three credit-reporting bureaus, “deceptively marketed credit scores to consumers by misrepresenting” them as “the same” as what their lender would use in determining whether and on what terms to offer them a loan.

In fact, said the bureau, the scores Experian advertised extensively were its own proprietary “educational” scores that virtually no lenders use to make credit decisions.

Experian’s promotions appeared on third-party websites, banner and display ads, direct mailings and sites such as FreeCreditScore.com, FreeCreditReport.com and CreditReport.com, as well as AnnualCreditReport.com.

[More Harney: Paying a lot for an appraisal? A middleman may be getting a large part of the fee. ]

As part of the settlement, Experian was fined $3 million. The case follows Consumer Financial Protection Bureau settlements in January over similar allegations with the other national credit bureaus — Equifax and TransUnion — in which they were required to make $17.6 million in restitution to consumers and pay $5.5 million in fines. TransUnion and Equifax were accused not only of falsely representing the usefulness of their in-house educational scores but also luring consumers into “costly recurring payments for credit-related products with false promises.” All three bureaus denied any wrongdoing.

Which brings us back to mortgages. If you’re like many home buyers and owners, you’ve seen online pitches and ordered your scores, often free. They may have come with tie-ins to credit card offers or credit monitoring and identity-theft-protection services.

One site may have said your score is 788, ranking you as “excellent” on their scale. Another may have said you look even better — your credit score is 801 and you’re among the credit elite.

Armed with these seemingly sterling scores, you start checking out mortgage company offers. With an 801, you figure, hey, I’m bulletproof. I’m a prime candidate for the best mortgage deals out there.

Then you apply to a lender for a preapproval and get the sobering news: Your middle FICO score — lenders often pull scores from all three bureaus — is a 716, and that’s what we’ve got to use to price your loan. The score is okay, but it’s 85 points below where you thought you were and below the cutoff point for the best mortgage interest rates and terms.

[More Harney: For many millennials, FHA is the place to go for a home mortgage]

FICO scores, which are predominant in the mortgage market and mandated by giant investors Fannie Mae and Freddie Mac, run from 300 to 850. Higher scores mean lower risk to the lender. Lower scores can cost you a lot. According to a March 23 national survey for FICO by Informa Research Services, a mortgage applicant with a 765 FICO would get an average quote of 3.8 percent on a $300,000 loan with a monthly principal and interest payment of $1,405. The same applicant with a 650 FICO would be quoted an average rate of 4.9 percent with a monthly payment of $1,589 — $184 more a month.

But here’s a little complication: The FICO score your lender pulls for your mortgage application might not be the same as the FICO score your credit card company might be sending you every month online. Or, perplexingly, it might even be different from the FICO score you get on MyFICO.com.

That’s because FICO has introduced multiple models over the years, each with what the company describes as consumer-friendly improvements. The latest is FICO 9. The most widely used is FICO 8.

But most mortgage lenders use the older models specified by Fannie Mae and Freddie Mac. The differences in scores from older to newer may be modest for many applicants, but could be significant for some. Fannie and Freddie are considering updating their scoring models but have not done so yet.

Bottom line: Ask your loan officer which model was used to generate your FICO scores. And never depend on generic scores available online as part of your mortgage planning process.

Ken Harney’s email address is kenharney@earthlink.net.