What does “endorsement” mean on 12306?

“Endorsement” is 12306's literal translation of gaiqian — changing your train. It covers changing the date, the train number, or the seat class, and the official rules put three hard limits on it. Nothing about the word suggests “change my train” to an English speaker, which is why it ends up on every confused-foreigner list.

The official definition and its three limits

Per 12306's own English FAQ: “Endorsement refers to the procedures to take when passengers change the date of travel, train number, or seat (berth).” The limits that matter:

• Stations are frozen. You can change when you go and in what seat — not where from or to (the only exception: stations within the same city).
• Once per ticket. A ticket can be endorsed exactly one time. Choose the new train carefully; there is no second change.
• The refund trap. A ticket endorsed after train departure cannot be refunded at all — endorsement after departure is a one-way door, which is why the missed-train rescue starts with “don't touch the refund button.”

Paying the difference works both ways: a pricier new train charges the fare gap; a cheaper one refunds it, minus the standard refund service fee on the difference. During the Spring Festival peak season, a changed ticket's refund is charged a uniform 20% regardless of timing.

How to actually endorse

Before departure, endorsement is a two-minute flow in the 12306 app (or a Trip.com booking's change screen); after departure it's the station ticket window, same-day departures only. Tickets open ~15 days ahead on 12306 — the full booking flow, verification quirks and station tactics are in the trains guide, and the rest of 12306's odd vocabulary (“verification”, “waiting list”, seat classes) is decoded in the 12306 dictionary.