Question:  What documentation does the bank need on a money services business?

Answer:  According to FinCEN, you need the acknowledgement letter from the IRS Detroit Computing Center.  Merely checking the online site (msb.gov) for lists of registrants is probably not enough.  Confirm that the customer has registered or obtained a license (if needed) with the Texas Department of Banking (http://www.banking.state.tx.us/asp/msb/lookup.asp).  Comply with your CIP rules.