Don't confuse the UCC definition (which is the one that applies to your question) with the definition in Regulation CC.
Here's the definition of cashier's check in the Oklahoma UCC, section 3-104(g): "Cashier's check" means a draft with respect to which the drawer and drawee are the same bank or branches of the same bank.
And here's the Regulation CC definition, from §229.2(i):
(i) Cashier's check means a check that is--
(1) Drawn on a bank;
(2) Signed by an officer or employee of the bank on behalf of the bank as drawer;
(3) A direct obligation of the bank; and
(4) Provided to a customer of the bank or acquired from the bank for remittance purposes.
The 4th element of the Reg CC definition would exclude an expense check, so that it would not be a next-day item under 229.10(c)(1)(v). But the UCC definition doesn't include that splitting of hairs, so the expense check would be considered a cashier's check for the purposes of the UCC, such as the §3-312 procedure for claims relating to lost, stolen or destroyed cashier's, teller's and certified checks.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8