> But who can audit the reporting?

The same people that audit your taxes, roughly with the same consequences for lying. Except the IRS is far more likely to send unannounced auditors to NGOs than they are to send them to for-profit companies or individuals. It's more of a hassle to get/retain tax-free status than it is to simply pay your taxes like everyone else (as it should be).

> Is that it?

Let me guess: you haven't clicked on "view filing", which leads to a roughly 20-pages-long document.

Caught me :)