Certified funds are monies that are guaranteed by the bank. When a bank issues certified funds, the monies are already taken from the customer's bank account and are guaranteed to be available to the creditor, according to About.com.
According to Select CD Rates, a bank can disperse certified funds as a certified check, cashier's check, money order or wire transfer. In each of these instances, the funds must be immediately available and given to the bank before the bank can issue the certified funds payment.
The Missouri Department of Insurance explains that a certified funds payment may be required for some large purchases, such as the down payment for purchasing a home, as a method of guarantee of funds for the seller.