While there are many newer FICO versions, for home mortgages, FICO Score 5 is based on Equifax data, FICO Score 4 is based on TransUnion data, and FICO Score 2 is based on Experian data. Your mortgage FICO score is the middle of these scores. Fannie and Freddie currently only accept these FICO versions. Moreover, if, for example, you go directly to TransUnion you’ll get a VantageScore, not a FICO.