It seems to me that we could potentially have several MLOs involved in one application, i.e., the Banker in the branch who takes the application, the processor who receives the application and sends out the disclosures, and the Banker who closes the loan. Do all of these MLOs need to communicate their unique identifier?

The MLO should disclose their identifier in the first written correspondence before acting as an MLO. So if all the MLOs involved in the loan are going to give the customer some paper, they should also give the customer their identifier with the first written correspondence.

Best way to do that, the first interaction the MLO has with the customer....give out the MLO's business card with their identifier printed on it.