Permits and Lender Requirements for Conventional Loans

For all of us Realtors, I just heard today...we must be aware whether we are representing the buyer or seller that the seller must have permits for all the remodeling work that was performed on the house since the ownership.  Conventional lenders are now requiring copies of signed off permits on all work on the home before they will lend.  What are your suggestions when dealing with a seller who is resistant in obtaining copies of the permits because the square footage doesn't match what's on the County Records?  What would you do?  I would greatly appreciate your expert knowledge in this area.