Here's our situation and really need some advice. My question is related to loans that are run through Fannie's DU

Joint borrowers: Representative credit scores of borrower 1:-615 & borrower 2-645 Average median credit score of 630

Fannie's DU uses average median credit score to determine if the loan is approve/eligible but uses the representative credit score for pricing and loan delivery

In the example above, Fannie would give an approve/eligible since the average median credit score is 630 (above 620)
When the loan goes to U/W, they review items within the credit bureau (the actual credit score isn't reviewed again), property, DTI, etc. and may deny the loan for one of those reasons.

My question is for HMDA reporting purposes, what credit score is reported? The average median credit score of 630 since that is what triggered the approve/eligible in Fannie's DU or is 615 reported since it's the lowest of the representative credit score since that is what is used throughout the rest of the loan process (mortgage insurance, pricing & loan delivery)

You report the credit score relied on in making the credit decision. It sounds like 630 was used to qualify the borrowers, so that's what you'd report. If a different score is used for pricing, that wouldn't be reported. See 1003.4(15) and its commentary.