If you are wondering if the invoice or bill you received by mail is legit, please read on.
Scammers consistently target US trademark applicants and registrants. Many of those have names bearing a close resemblance to the name of the United States Patent and Trademark Office (USPTO) such as Patent and Trademark Office, LLC.
First off, if you have hired a U.S. attorney to work on your trademark application, you can safely ignore all but your attorney. The USPTO do not contact trademark owners directly when it has other contacts such as an attorney of record.
Second, the renewal of trademark registration requires paperwork. You simply cannot extend the life of a trademark registration by just footing a bill. Hence, the USPTO never sends you a bill; instead, it accepts filing fees along with required paperwork.
Lastly, this goes without saying. But when you are in doubt, do not pay!