What happens when a muffed punt goes into the endzone?

Answer 1

The receiving team can run it out or down it in the end zone for a touchback; if nobody on the receiving team touches the ball, that's also a touchback and the receiving team gets the ball first and ten on their own 20 yard line.

Answer 2

If the ball is punted and lands in the endzone then tipped back by the kicking team, it is ruled a touchback.

Answer 3

it's a safety

Answer 4

it is a touchback