The USPTO examines every application for compliance with federal law and rules. The most common reason to refuse registration is a “likelihood of confusion” between the mark of the applicant and a mark already registered or in a prior-filed pending application owned by another party. The USPTO determines that a likelihood of confusion exists when both (1) the marks are similar, and (2) the goods and/or services of the parties are related such that consumers would mistakenly believe they come from the same source. Similar marks or related goods/services by themselves are not enough to support a finding of a likelihood of confusion, unless a court has held that the mark is actually a famous mark. That is, generally two identical marks can coexist, so long as the goods and services are not related.
Each application is decided on its own facts and no simple mechanical test is used to determine whether a likelihood of confusion exists. Therefore, before filing your non-refundable application, it is very important for you to determine whether your proposed mark is likely to cause confusion with another mark. This determination can be made only after doing a thorough trademark search.