S-3 Filing
  
Dealing with the SEC is a headache. Some companies just stay private to avoid the paperwork. Public companies have to file all sorts of documents with the SEC.
The S-3 is one of the least odious filings a company makes. Touted as the "most simplified registration form" the SEC offers, it comes into play after a company has already fulfilled a number of requirements (and filed a bunch of other paperwork). It's used after IPOs, and for other offerings of common or preferred stock.