What is a tax filing extension?

An individual who files Form 4868 by the regular due date (usually April 15) gets an automatic extension to file their federal return, normally to October 15. Businesses use other forms, such as Form 7004.

The extension doesn't extend the time to pay. Tax owed is still due by the original deadline, and interest (and possibly a late-payment penalty) applies to any balance paid later, so an extension usually comes with an estimated payment.

For firms, extensions are a planning tool: clients waiting on late documents, such as K-1s, can be extended early instead of crowding the last week before the deadline. State extension rules vary. This is general information, not tax advice.

Free resource: Client tax document checklist.