As a referee, your job doesn’t end when you blow the final whistle. Leagues require you to fill out a game report within 48 hours of the match (ask your assignor if you don’t know how to do this). If you have any misconduct and show any yellow or red cards- then you must also fill out a USSF match report.
If you only showed yellow cards, you have to fill out the Game Report. If you had a send off, then you must fill out the Game Report and the Supplemental Report. Showing a red card also means you only have 24 hours to get your reports in so the disciplinary committees can do their job in a timely manner. You can find these reports on the Forms page.
Failure to get your reports done on time will probably result in you not getting paid for the match. Your Assistant Referees will still get their money, but you will be left out- because you didn’t finish your job.
When you fill out any report, you should consult the Cautionable_and_Sending_Off_Offenses document. Make sure your reason is listed. There are only 7 reasons you can show a caution and 7 reasons you can send some one off. Make sure you get it right.