Once your trademarks registers, there are renewals and other filings that must be filed with the trademark office periodically. Recently, there has been a rash of unsolicited letters by "services" claiming that trademark owners owe, in some cases, thousands of dollars in "renewal" or "registration" fees. The letters provide bank and account wiring instruction and are written in a manner that suggests the letters are from an official government or other agency (i.e., either in the United States or abroad). If you receive these types of letters, please have your attorney or representative review them, since the letter is most likely a scam and once you pay it's money lost. That is one of many reasons why you should work with experienced attorneys and counsel on your intellectual property matters to make sure that (a) your filings are properly prepared, (b) all challenges to your trademark application are responded-to properly, and (c) you're protected from the rising instances of trademark scams.