There really isn't a need to certify a bank official check. And I'm assuming that "bank offical check" means something like a cashiers check or money order.
A certified check is a check drawn on a customer's account upon the face of which the bank has stamped "certified" with the date and signature of a bank official. This certifies that the monies are, indeed, collected funds. The monies should be transferred from the customer's account to a separate liability account of the bank, with the check becoming the direct liability of the bank. Otherwise, as we all know, just because someone writes us a personal check doesn't mean the money they wish to give us is actually collected and in the bank at the time we receive the check. It is illegal for a bank to certify a check without collected funds actually on deposit at the time of the certification.
Official checks, on the other hand, are instruments of the bank drawn on itself. Customers may purchase these, such as a cashier's check, with collected funds. They are used to increase the negotiability in commercial transactions by substituting the name and credit of the bank for that of a lesser known party. Anyone receiving a cashier's check or bank money order is assured that the funds are collected, absent some fraud.
So, certifying a bank offical check is kind of redundant. AR.