Thanks! I'm also working on a SAR now where we have a non-customer (subject) who is cashing on-us checks payable to him. We would list the on-us account number in Item 27, correct? Reading the SAR instructions, it says "An account is related to a subject if the subject owns the account, has control over the account, or conducted activity in or through an account the subject does not own or control." So I would think I would enter that on-us account number as being related to him since activity is being conducted through the account.
(Sorry, started a new job and things are being done differently here than at my previous bank and it's really creating a lot of headaches for me!)