It's both, though the requests are automatic when timely filed.You need to file an 8832 (to elect to be taxed as a corporation) and a 2553 (to elect that corp to be taxed as an S corp).For calendar year entities both forms are due March 15 of the year you want it to be effective. Otherwise within 75 days of the beginning of the effective year.If you miss the due date there are various revenue procedures to follow in order to submit a late election. I have found the IRS to be quite liberal with granting late elections.