I am guessing what you are talking about is that most lenders require verification documents for issuing preapprovals. Currently under RESPA, and soon to be Reg Z, you can’t require verification documents for issuing a GFE/loan estimate. I believe there has been some concern that lenders can’t obtain the verification documents and therefore can’t issue a pre-approval. I believe the general consensus is that as long as you don’t have all six pieces of information that constitute an application then you don’t have an application then you don’t have application for TRID purposes and therefore the LE isn’t triggered. In that case you could ask for verification documents for the pre-approval, but if the potential borrower has provided you all six pieces of information it becomes an application for TRID purposes and you can’t require verification documents in order to issue the LE.
There is some discussion on this in the commentary and preamble to the integrated disclosure rules (located on the CFPB’s website). You can also google “TRID and preapproval” and find a lot of information.
Keep in mind that even though you may not have an application per the TRID rules you may still have an application under Reg B and you may need to follow those rules accordingly.