IRS filing deadlines depend on the requested effective date and the entity's circumstances. Because late-election relief may be available in some situations, current IRS instructions should be reviewed for the applicable deadline.

An S corporation should be explained as a federal tax classification rather than simply another state entity type. A qualifying corporation or LLC can seek S corporation tax treatment by making the required federal election. The entity must satisfy eligibility rules, and the underlying state-law entity continues to exist as the corporation or LLC that was formed with the state.