The U.S. Patent and Trademark Office will deny an application for federal trademark registration if the trademark is “likely to cause confusion” with a prior registration. This inquiry mainly boils down to whether the marks and associated goods or services are sufficiently similar that ordinary consumers would mistakenly believe that the applicant’s goods or services come from the registrant, or vice-versa.
There are strategies that can minimize the chance of drawing this objection. For one thing, you can be smart in describing your goods or services. Describing them in narrow terms can avoid an appearance of being closer to a prior filing than you need to be. That sometimes works.
One thing that doesn’t work is adding or deleting a space between tradmark elements (TRADEMARK vs. TRADE MARK) or adding a “.COM” suffix to the dominant part of the mark. The USPTO largely ignores spacing and domain name extensions when evaluating likelihood of confusion. As it should — consumers don’t focus on such small details when deciding which product to buy.
Hats off to trademark owners who think about these things. But when a target trademark is close to a registered mark, a meaningful change — like adding a distinctive trademark element — is usually required to avoid a likelihood of confusion objection.