Legal Question in Family Law in North Carolina

You don't need any proof to file for divorce in North Carolina. However, you do need to be eligible. In North Carolina, either you or your spouse must have lived in NC for at least 6 months prior to filing for divorce AND you must have been physically separated (not living together for a period of one year with the intention not to resume the marital relationship. When you file for divorce you will sign a divorce complaint under oath that has statements regarding your eligibility - that's all the proof you need to file.

I suspect two things: 1) you haven't been separated for the required year period of time and 2) your real question isn't about the proof needed to file as you stated but rather the proof of the cheating. When it comes to proof of cheating there are lots of ways to prove it. Video, audio, private investigators, your spouse's own addmissions ect.