What is the law that states that servicers and banks have to give borrowers at least 15 days notice of transfer/sale of mortgage

The Real Estate Settlement Procedures Act (RESPA) requires a mortgage servicer to give a notice of transfer of morgage servicing. See 12 USC § 2605; 24 CFR 3500.21. The notice must be given by the transferor not less than 15 days prior to the effective date of the transfer of the servicing of the mortgage loan. The transferee must deliver the notice not more than 15 days after the effective date of the transfer of the servicing of the mortgage loan. Both the transferor and the transferee may elect to send one combined notice that must be given not less than 15 days prior to the effective date of the transfer of the servicing of the mortgage loan. A notice of transfer is only required to be sent to those customers that have residential mortgages secured in a first lien position. A notice of transfer is not required if there is no change in the payee, address to which the payment must be delivered, account number or payment amount and if the transfer results from one of the following: (i) a transfer between affiliates, (ii) a transfer resulting from the merger or acquisition of a servicer or subservicer, or (iii) a transfer between a master servicer, where the subservicer remains the same. In this case, you will need to contact the transferror and the transferree to verify the actual date in which servicing will transfer. It is unlikely that there is an intervening owner of your loan. Regardless of the date servicing transfers, you should continue to make your payments as required under the loan documents. If an issue arises with the application of any of your payments following the transfer of servicing, you should immediately send a Qualified Written Request to the new servicer with a complete description of your dispute.

The Real Estate Settlement Procedures Act (RESPA) condified at 12 U.S.C. 2601 et seq. is the law that applies to servicing transfer notifications. The owner of the loan need not be the servicer of the loan and vis-a-versa. Therefore, it is possible that the loan was sold effective as of April 16, but that the new servicer wasn't appointed until April 21. To determine who the proper owner is, I recommend contacting the new servicer. Good luck.