I am searching for the rules regarding the trigger for underdisclosure and when a new TIL has to be given. Is there a dollar amount associated with this? I thought it was 100.00 but now I can't find that in the RESPA rules. Please let me know if you have any idea where I can find this quickly!

It is actually in the Reg Z rules under Sec 226.18 Content of disclosures. Item (d)(1) Mortage Loans