"Likelihood of Confusion" is a legal basis that the U.S. Patent and Trademark Office (USPTO) may use to refuse registration of a trademark or service mark because it is likely to conflict with a mark or marks already registered or pending before the USPTO.

After a trademark application is filed, the assigned USPTO examining attorney will search the records to determine if such a conflict exists between the mark in the application and another mark that is registered or pending before the USPTO. The USPTO will not conduct any preliminary searches for conflicting marks before an applicant files an application and cannot provide legal advice on whether a particular mark can be registered.

The principal factors considered by the examining attorney in determining whether there is a likelihood of confusion are: (1) the similarity of the marks; and (2) the commercial relationship between the goods and/or services listed in the application.

To find a conflict, the marks do not have to be identical, and the goods and/or services do not have to be the same. It may be enough that the marks are similar and the goods and/or services related. If a conflict exists between your mark and a registered mark, the examining attorney will refuse registration on the ground of likelihood of confusion. If a conflict exists between your mark and a mark in a pending application that was filed before your application, the examining attorney will notify you of the potential conflict and possibly suspend action on your application. If the earlier-filed application registers, the Examining Attorney will refuse registration of your mark on the ground of likelihood of confusion.