Written by The Commonwealth Group
Underwriting guidelines change rapidly. For the most up-to-date information, please refer to the Fannie Mae Selling Guide at Selling Guide | Fannie Mae or for Freddie Mac at Guide Home. This post focuses on Fannie Mae requirements. The Selling Guide text has not yet been fully updated for the September change, so this post relies on Lender Letter LL-2026-06 and the current Guide sections cited below.
For decades, "what is the credit score?" had one practical answer for a conventional loan. Classic FICO was the language of the agencies, and every process in the building, from the credit vendor to the pricing engine, was built around it. On September 9, 2026, Fannie Mae changed that with Lender Letter LL-2026-06: VantageScore 4.0 is now available to all Fannie Mae-approved lenders, effective immediately, without prior written approval.
Choice sounds like good news, and it can be. But every choice in a loan file is also a place for a defect to hide. Here is what the letter allows, what it requires, and where a QC review should look.
What the Letter Says
The following points come from LL-2026-06. They are worth reading in the letter itself, because the Selling Guide section on credit scores, B3-5.1-01, General Requirements for Credit Scores, still describes the earlier limited rollout and has not yet caught up.
Open availability. Any approved lender may originate and deliver eligible loans using VantageScore 4.0. A lender not ready may keep using the eligible Classic FICO models.
DU accepts it. Desktop Underwriter accepts VantageScore 4.0 credit reports on all casefiles underwritten through DU Version 12.1, from Equifax, Experian, and TransUnion.
All three bureaus. A lender that elects VantageScore 4.0 must request it from each of the three repositories when ordering a new credit report. The existing rules on unavailable scores, insufficient credit, and frozen credit still apply.
One model per loan. The lender may choose Classic FICO or VantageScore 4.0, but the same model must be used for all borrowers on the loan.
Manual underwriting stays Classic FICO. Lenders must continue to use only Classic FICO for manually underwritten loans and meet the minimum scores in the Selling Guide and Eligibility Matrix.
Pricing. The LLPA Matrix now includes pricing for VantageScore 4.0 loans.
Delivery. Deliver the representative score and other required score data, make sure the model used for underwriting and pricing is accurately reflected in the loan data, retain the score information in the file, and deliver Special Feature Code 067 on any loan originated with VantageScore 4.0.
FICO 10T is not yet deliverable. The letter says FICO Score 10T is not currently eligible for delivery.
How the Representative Score Still Works
The steps in B3-5.1-02, Determining the Credit Score for a Mortgage Loan have not changed. With three scores for a borrower, use the middle score. With two, use the lower. When there is more than one borrower, the representative score for the loan is the lowest applicable score from the group. Because the model must be the same for every borrower, you cannot mix a borrower's VantageScore with a co-borrower's Classic FICO to land on a better number.
Putting Numbers to It: One Loan, Two Borrowers
The figures below are hypothetical and are shown only to illustrate the steps.
Borrower A, VantageScore 4.0 from three bureaus: 702, 688, and 695. The middle score is 695.
Borrower B, VantageScore 4.0 from three bureaus: 721, 715, and 709. The middle score is 715.
Representative score for the loan: 695, the lowest of the two borrowers' middle scores. That is the score that drives the LLPA grid and must be delivered.
If a team accidentally ran Borrower B on Classic FICO and received a different set of scores, the file would no longer meet the one-model rule, and the pricing and delivery data could not be trusted. Nothing about the borrower changed. The defect is purely in the process.
Where QC Finds the Defects
Mixed models. One borrower on VantageScore 4.0 and another on Classic FICO.
VantageScore 4.0 on a manually underwritten loan. The letter says manual underwriting stays with Classic FICO.
Missing Special Feature Code 067. The loan was originated on VantageScore 4.0 but delivered without the code.
Pricing and data mismatch. The LLPA, the representative score, and the model flag in the delivery data do not agree with the credit report in the file.
Incomplete bureau pull. VantageScore 4.0 was ordered from only some repositories.
Credit report not retained. The Guide requires the report to be kept in the file, including reports that show no score because of insufficient or frozen credit.
Frozen credit handled loosely. A freeze at one repository is acceptable if data is available from two. A freeze at two or more makes the loan ineligible, manually or in DU.
Wrong minimum applied. DU casefiles have no minimum score requirement, but manual loans do: 620 for fixed-rate and 640 for ARMs, per the Guide.
The "Why" Behind the VantageScore Refresher
A new option does not remove old rules. It adds new ways to violate them. The representative score determines price, eligibility on manual loans, and what the buyer thinks it is purchasing. If the model in the file, the model in the pricing engine, and the model in the delivery data are three different things, that is a repurchase conversation waiting to happen.
The Commonwealth Group: Precision. Integrity. Results.
When the rules of credit scoring change, your team needs a partner who reads the letter, not just the headline. At The Commonwealth Group, our contract underwriting and quality control teams check the model, the score, the pricing, and the delivery data against each other so the loan you close is the loan you can sell. We do not just follow the guide; we know what to do when the guide is not enough.
Ready to go beyond the guide?
Contact Martin Luplow at The Commonwealth Group – info@thecommonwealth.net for more information on what our team of professionals in processing and underwriting can do for your company.
The Commonwealth Group – Innovative Services for the Mortgage Industry
West Beibers, CMB, AMP, CRU
Chief Executive Officer
The Commonwealth Group Companies