Not the one in your banking app: a mortgage file pulls all three bureaus and uses older FICO models built for mortgage lending, one per bureau, then takes the middle of your three scores, and where there is a co-borrower the price of the loan has been set off the lower of the two middle scores.
People are surprised twice. First that the number the lender quotes is lower than the one they have watched for months, and second that it comes from a model they have never heard of. Both have one cause: mortgage lending runs on its own scoring stack, held years behind consumer apps by the agencies that buy the loans, and it is being replaced slowly and in public.
Three bureaus, three scores, and the middle one
A mortgage lender orders a tri-merge report, which pulls Equifax, Experian and TransUnion at once and returns a score from each. The models are the classic FICO versions each bureau supplies for mortgage use, and they are different versions on each bureau rather than one score computed three times. Your files at the three bureaus are also not identical, because a creditor may report to two of them and not the third, so a spread of 20 or 30 points between them is ordinary.
The lender then takes your middle score, not the average and not the best. With a co-borrower, each person's middle score is found the same way, and the loan has historically been priced off the lower of them, which is why one applicant with thin credit sets the cost for both. The agencies have added an average of the borrowers' median scores for testing whether a manually underwritten file clears the minimum, so the exact treatment now depends on how the file is underwritten, and it is in transition.
Why it differs from the score in your app
Two reasons, and neither is an error. The model is different: a free score is usually a VantageScore or a consumer-education FICO version, tuned for general credit rather than mortgage default, while the mortgage versions are older and score some behaviour more harshly. The date is different too, because an app score refreshes weekly against one bureau while the lender's pull is a fixed snapshot of all three on the day it was ordered. The app score is useful for watching a trend and useless as a figure to plan a rate around.
The move to newer models, still in progress
The Federal Housing Finance Agency approved FICO 10T and VantageScore 4.0 for the agencies in 2022, and the change has been rolling out slowly since. VantageScore 4.0 has become usable for conventional loans through approved lenders, historical FICO 10T data has been published so lenders and investors can model it, and classic FICO remains an approved model throughout. An earlier plan to drop the third bureau and allow a two-bureau report was reversed, so the tri-merge requirement stands.
What that means for a borrower is that the score behind your loan may be computed by a different model than the one behind a loan closed last year, and the newer models weigh trended data, meaning whether balances have been climbing or falling over 24 months rather than the balance on one day. Nothing in the transition changes what improves a score: paid on time, balances low against limits, nothing new opened during the file.
How the score prices the loan, not just approves it
Credit score is not a gate with one threshold. On a conventional loan the agencies publish a grid of loan-level price adjustments, and the score band and the loan-to-value band together set a cost that is either paid in points at closing or built into the rate. The same loan at a 780 score and at a 660 score is not the same price, and the gap between bands is largest where the down payment is smallest.
Government loans behave differently. FHA sets its mortgage insurance premium by loan-to-value and term rather than by score, so a lower score costs less there than on a conventional loan, which is why the comparison between programs shifts as the score moves. A specific rate, on a specific day, at a specific score, is a quote and not something this page can give.
Questions people ask
Do mortgage lenders use the middle or the lowest credit score?
The middle of your three bureau scores, for each borrower individually. Where two people apply together, the loan has been priced off the lower of the two middle scores, so the stronger file does not lift the weaker one for pricing purposes.
Does applying with more than one lender hurt your credit score?
Mortgage inquiries pulled within a short shopping window are treated as a single event by the scoring models, so rate shopping is not penalised the way opening several new accounts is. The window is measured in weeks, and the models differ slightly on its length.
How long is a credit report good for on a mortgage file?
Lenders work to a document age limit and typically require the credit report to be recent at closing, redrawing it if the file drags on. Many also run a soft refresh just before funding, which is why opening a card mid-escrow can undo an approval.