How do you get Return to Sender in Minecraft?

Find a ghast: they spawn in nether wastes, soul sand valleys and basalt deltas.

What kind of advancement is Return to Sender?

Return to Sender is a Nether tab advancement in Java Edition, of challenge type, rewarding 50XP experience.

Return to Sender

Tab: NetherChallengeReward: 50XPDifficulty: Medium

Quick answer: Destroy a Ghast with a fireball

Tree path: Nether › Return to Sender (advancements are independent: they can be completed in any order; the tree only guides progression)

Tree parent: Nether

Advancements are exclusive to Java Edition. The Bedrock Edition equivalent is achievements, which have different objectives.

How to get Return to Sender

Find a ghast: they spawn in nether wastes, soul sand valleys and basalt deltas.
Wait for it to shoot a fireball at you, then hit the fireball back with any melee attack, or shoot it with an arrow or another projectile. The reflected fireball flies back in the direction you are aiming.
Kill the ghast with its own reflected fireball. A reflected fireball that connects kills a ghast in a single hit, so this is about aim, not damage.
The advancement (and 50 XP) is yours the moment the ghast dies to its own shot.

Tips

Swing just before the fireball reaches you and keep clear line of sight. The open nether wastes are the easiest arena: no terrain for the ghast to hide behind, and you can see the shot coming from far away.

Advancements this unlocks

Uneasy Alliance (100XP XP)

More guides from this tab (Nether): Nether Those Were the Days Hidden in the Depths Subspace Bubble A Terrible Fortress Who is Cutting Onions?