WHAT'S NOT INCLUDED IN YOUR TRADEMARK APPLICATION FEE?
Responding to substantive office actions or oppositions from third parties are not included in the initial fixed price fee. Not all applications receive office actions from the USPTO, but many do.
Also, if your application is a 1(b) "Intent to Use" application, you will be asked to pay an additional USPTO fee ($100 per class as of Jan, 2021) when the Statement of Use certification is filed later in the application process.
Although more uncommon, other additional fees could be incurred during the application process.