Money orders are a safe alternative to cash or checks. Find out how much they cost, when you need one, where to buy it and how to cash it.Filling out a money order is a straightforward stepbystep process. Just follow these instructions and you'll be ready to send your money. Forms of payment accepted on The Postal Store®. VISA®; MasterCard®; Discover®; American Express™. Many retailers will not accept credit cards as a form of payment for money orders. Enclose your check or money order with the appropriate paper form and send via U.S. Mail. How did you find out about Us Express Money Order? Defaulted on American Express credit card.