DU in a mortgage stands for Desktop Underwriter, Fannie Mae’s automated underwriting system. When you apply for a conventional home loan, your lender feeds your application into DU, and within seconds the system returns a recommendation on whether the loan meets Fannie Mae’s standards for purchase on the secondary market. That recommendation drives what happens next: which documents you’ll be asked for, whether you can skip a traditional appraisal, and how close you are to a clear-to-close.
What Desktop Underwriter Does
Fannie Mae built DU to standardize how lenders evaluate credit risk before selling loans. Before automated underwriting, a human underwriter reviewed every file by hand, which could take days or weeks. DU replaces that first review with an algorithm that cross-references your financial data against Fannie Mae’s selling guide, producing a recommendation almost instantly.1Fannie Mae. General Information on DU
The system weighs your debt-to-income ratio, loan-to-value percentage, credit history, and other risk factors together. Because every application runs against the same rules, DU reduces the inconsistency of individual human judgment at the preliminary stage. A human underwriter still verifies the file, but DU sets the terms of that review.
What Information DU Looks At
DU only evaluates what your lender enters into the Uniform Residential Loan Application (Form 1003), so bad data produces an unreliable result. Expect your lender to ask for detailed records upfront in four areas:
- A three-bureau merged credit report pulled with your Social Security number, covering seven years of credit and public record history.2Fannie Mae. Requirements for Credit Reports
- A two-year employment history with documentation of gross monthly income, including base salary, commissions, and bonuses.
- Statements from checking, savings, and retirement accounts showing funds for the down payment and closing costs.
- All existing debts — student loans, car payments, credit card balances — so DU can calculate an accurate DTI.
Small mismatches matter. DU automatically compares the debts listed on your credit report against the debts you disclosed on the application, and any inconsistency will require your lender to resubmit the file.3Fannie Mae. Accuracy of DU Data, DU Tolerances, and Errors in the Credit Report
The Four Recommendations DU Can Return
Every DU Findings report ends in one of four results.1Fannie Mae. General Information on DU Each one tells you where your application stands.
Approve/Eligible
The result you want. The loan meets Fannie Mae’s credit risk standards and is eligible for sale to Fannie Mae, provided the lender verifies your data and satisfies the conditions in the Findings report.4Fannie Mae. Approve/Eligible Recommendations It isn’t an unconditional approval, but it’s a strong green light.
Approve/Ineligible
Your credit profile is acceptable, but the loan itself doesn’t meet Fannie Mae’s eligibility requirements. The loan terms, property type, or product features fall outside what Fannie Mae will purchase.5Fannie Mae. Approve/Ineligible Recommendations Your lender may be able to restructure the loan — adjusting the term, down payment, or product — and resubmit for a different result.
Refer with Caution
The risk profile is too high for automated approval. This is not an automatic denial. It signals that a human underwriter needs to review the file, and that underwriter may find compensating factors like large cash reserves or a strong payment history. Manual underwriting comes with stricter requirements, including a minimum credit score of 620 for fixed-rate loans and 640 for adjustable-rate mortgages.6Fannie Mae. General Requirements for Credit Scores
Out of Scope
The loan falls entirely outside what DU can evaluate, usually because of the product type or loan parameters. Your lender will need to look at manual underwriting or a different loan program.
Credit Score and DTI Thresholds Inside DU
DU does not enforce a minimum credit score. It weighs multiple risk factors together rather than applying a single floor.6Fannie Mae. General Requirements for Credit Scores A very low score still increases the chance of a Refer with Caution result, and most lenders set their own internal minimum, commonly around 620, even though DU itself doesn’t.
Debt-to-income is a harder ceiling. DU caps approval at 50%. If your total monthly debt payments including the proposed mortgage exceed half your gross monthly income, DU will not return an Approve/Eligible recommendation. High-LTV refinance transactions have no maximum DTI under certain conditions.7Fannie Mae. Debt-to-Income Ratios
When DU Waives the Appraisal
For some loans, DU offers “value acceptance,” meaning a traditional appraisal isn’t required. If your final submission comes back with a value acceptance offer, your lender can skip the appraisal, saving both time and money.8Fannie Mae. Value Acceptance
On purchase transactions for primary residences and second homes, value acceptance is available at loan-to-value ratios up to 90%, a threshold that was raised from 80% starting in early 2025.9Fannie Mae. Value Acceptance Not every loan qualifies. DU decides based on the property, the data available for it, and the loan’s overall risk profile. A separate option called Value Acceptance + Property Data allows higher LTVs up to program limits but requires the lender to collect property data in place of a full appraisal.
When Your Lender Has to Rerun DU
The initial DU submission isn’t always the last. Certain changes during processing require your lender to resubmit for a fresh recommendation:
- An interest rate increase. A rate decrease only triggers resubmission if it comes from a permanent buydown.
- New debt you take on during the process, or debt the lender discovers that wasn’t on the original application.
- A recalculated DTI that now exceeds 45%, or that rises by 3 percentage points or more while staying at or below 50%.
- On refinances, a loan amount increase greater than $500 or 1% (whichever is less), or a decrease greater than 5% if the change affects mortgage insurance or eligibility.3Fannie Mae. Accuracy of DU Data, DU Tolerances, and Errors in the Credit Report
This is one reason lenders warn you not to open new credit accounts or finance a car between application and closing. A single new tradeline can force a resubmission and possibly a different result.
How Long DU Findings Stay Valid
DU findings expire with their supporting documents. Credit documents, including income, employment, and asset records, must be no more than four months old as of the date you sign the promissory note. If closing gets delayed and documents age out, your lender has to refresh them and may need to resubmit.10Fannie Mae. Allowable Age of Credit Documents and Federal Income Tax Returns
Where consecutive documents are used, such as two monthly bank statements to verify assets, the most recent statement must land inside that four-month window. The credit report has its own age requirement as of the note date, and if it expires before closing, the lender must pull a new one before resubmitting to DU.1Fannie Mae. General Information on DU
DU Is Not the Only Automated System
Freddie Mac runs its own automated underwriting platform called Loan Product Advisor (LPA). Many lenders submit the same application to both systems to see which returns a better result. LPA uses a two-tier classification of Accept or Caution, compared to DU’s four recommendations, and has its own appraisal-waiver equivalent called Automated Collateral Evaluation.11Freddie Mac Single-Family. Loan Product Advisor If DU returns a result you don’t like, ask your lender whether running the file through LPA would help. The two systems apply different guidelines, and the same borrower can get different answers from each.