What is Tax Extension (Form 4868)?
Filing Form 4868 buys individuals six extra months to file a return — moving the deadline to mid-October. It does not give you more time to pay.
How it works
You file the extension by the April deadline and it's automatic — no reason required. But any tax you owe is still due in April, so you estimate and pay it then to avoid interest and penalties on the balance.
A quick example
What people get wrong
An extension to file is not an extension to pay — the single most misunderstood point in taxes. File on time even if you can't pay, and pay as much as you can, because the late-filing penalty is ten times harsher than the late-payment one.