From the manual:
If the purchaser does not have a deposit account with the bank:
Name and address of the purchaser.
Social Security or alien identification number of the purchaser.
Date of birth of the purchaser.
Date of purchase.
Types of instruments purchased.
Serial numbers of each of the instruments purchased.
Dollar amounts of each of the instruments purchased.
Specific identifying information for verifying the purchaser’s identity (e.g., state of issuance and number on driver’s license).
All of this must be kept for 5 years.
Link:
https://www.ffiec.gov/bsa_aml_infobase/pages_manual/OLM_023.htm