[kanamekun]

Other posters are correct; you are obligated under US law to report child porn to the NCMEC CyberTipline.

The fine for not complying started off fairly low, but has been increased in subsequent legislation. In my experience though, NCMEC is mostly just interested in getting regular reports uploaded to their system. I met with them once, and they have a rough sense for how many reports should be sent over for a site of a certain activity/traffic level, and if the number of repots is zero... then they know you're not in compliance.

Their reporting interface is beyond awful though. Maybe they've improved it in recent years; when I last saw it, everything had to be uploaded and reported manually.

[mirimir]

Would it be enough to report content flagged by other users as CP? Is there a requirement to review content before submission? That's not something I'd ever want to do. I don't think that I'd want to pay someone else to do it either.

[kanamekun]

As I understand it, there's no requirement to review content before submission. My understanding is that once someone has flagged or reported it to you, you're mandated to report it.