The laws vary depending upon the office you run for.
As an example, if you are running for a position within Harris County you must file with Harris County Clerk at http://www.ethics.cclerk.hctx.net. The website has a link to the filing schedule hosted at the Texas Ethics Commission. This schedule for County races shows who must file and when.
There are a number of reasons to understand the laws concerning financing of a campaign. One, it is the law. If you miss a report, you will be called out for it and fined. And two, if you do not follow the law by missing reporting requirements or not filling out your reports correctly, this information could be used against you in your campaign. Don’t give your opponent the opportunity to say “If you can’t follow the law, how can you make the law?”.
It’s a good point. Know the law. Follow the law.