The action date used for a purchased loan is the date of the purchase. We don't get any more guidance than that . 12 CFR 1003.4(a)(8)(ii) and comment 4(a)(8)(ii)-6.
So, that could mean the agreed-upon date for the purchase, the date the purchase docs are signed, or the actual date funds are advanced to purchase the loan, I think. You would want to select what your bank means by "date of purchase" and stick to it.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8