As an Applicant for a patent, your information becomes public when the application publishes and once again when the patent itself issues. Unfortunately, there are several companies that mine this information for their own commercial or other purposes.
Following publication of an application, these companies will send out official-looking notices offering to register the patent application for a fee. This registration is not required by any official organization, nor does it provide any benefit to you. We do not advise responding to these third-party patent registration organizations.
Additionally, there are companies that will contact you with regards to the payment of maintenance fees. While maintenance fees are, in fact, due on pending applications and issued patents, as your counsel, Wilson Sonsini will communicate with you directly about maintenance fees unless you specifically instruct us not to handle such payments.
Examples of these problematic notices are located here.