A third-party transaction is a business deal that involves a person or entity other than the main participants. Typically, it would involve a buyer, a seller, and another party—the third party. The involvement of the third party can vary, based on the type of business transaction.

In some cases, the involvement is one-time, such as a third-party payment for an item purchased from a website. Sometimes the involvement is longer term, such as a third-party vendor always used by a certain company.