When a Trademark is Non Final Mark can you still use it?

There are common law rights that can exist before a Federal trademark registration application is filed. The answer to your question is not a simple one. It requires an analysis of who used the mark first in the relevant market, what goods or services were sold under the mark, and whether there is a likelihood of confusion between there use and your use. You could consider filing a trademark opposition proceeding if you were earlier in your use. Hire competent counsel to help you with this analysis.

You must use the mark in interstate commerce before the USPTO will grant the registration. If you apply for a provisional registration, you have one year from the date of application to use the mark in commerce. If you fail to use the mark in interstate commerce, the USPTO will not grant the registration.

It is more complicated than that. You can be held liable for infringing on someone's trademark during any part of the process. What matters is are you using a confusingly similar brand in commerce and have they established priority rights to their brand in the area where you are using it.

You can start to use a trademark before or after filing a trademark application.

You can use your mark whenever you would like and can place TM next to it as well, regardless of whether you have filed for federal registration. You can place the "circle R" next to your mark once the USPTO reviews and registers it on the TM Register.