Which of the following cannot be purchased with a credit card?

Money orders are a specific financial instrument that often has restrictions on how they can be purchased. In many locations, money orders typically must be purchased with cash, debit cards, or in some cases, check. This is due to the nature of money orders as a prepaid item that is designed for safe transactions, minimizing the risk of fraud.

In contrast, postage stamps can generally be purchased with a credit card through various outlets, including postal offices and online. Certified mail and Priority mail packages are also services provided by the USPS that can be paid for with a credit card, as they link to mailing services available for use by consumers. Thus, the unique purchasing restrictions associated with money orders make them the item that cannot be directly bought with a credit card in many instances.