Getting back to your question, under Regulation CC (which is what I believe you are asking about), a cashier's, teller's or certified check payable to more than one party is considered a next-day availability item if deposited to the account of a payee of the check. It doesn't have to be deposited to an account in the name of all of the payees [229.10(c)(1)(v)(A)] provided it's deposited with an employee of the bank with a special deposit ticket (if the bank requires the use of a special ticket to attribute next-day status to the check).
That said, I agree with Ken if the check is payable to multiple parties not in the alternative (use of AND or & between the payee names). But if the payees are named in the alternative (use of OR or a virgule or forward slash (/) or simply stacking the names up one over the other with no connecting text), any one of the payees has full rights in the check and an indorsement of any one of them is sufficient.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8