There is no charge to file for a Homestead Tax Exemption. And all primary residences in Texas are covered by state Homestead Protection laws. Homestead laws protect homeowners from losing their primary residences in bankruptcy or from lawsuits. You do not have to file any documents to have this kind of asset protected under the law.
A client of ours who bought a house last year received this very official-looking document in the mail. He asked me about it, not sure what it was for. It looks like a very important document from the state, or so it seems. It is a SCAM, a way to collect money under false pretense.