One of our customers has a tax refund check from the State of Oklahoma, we are located in Arizona. Can we hold this check for 5 business days? This is not a new customer and the check is less than $5,000. Check was deposited in person.

A state government check is only a mandatory next-day item when it is deposited in a bank in the state that issued the check. See 229.10(c)(1)(iv). In all other circumstances the check would be treated as an ordinary local or non-local item. In your case, a five day non-local hold seems perfectly legal.