When a trailer is certified, a certification notice is sent via email to you and the MPAA simultaneously, along with a Certification Number. Once received, that mix is compliant and certified. No further action or documentation is needed.
What about minor changes to the trailer?
A TASA certification certifies the audio mix made on that date. If the audio is adjusted in any way, it is considered a new mix and must be re-submitted for certification. However, any image changes (additional cards, video edits, etc.) that do not also change the audio would retain the TASA certification.