I am shipping MACBOOK AIR FOR REPAIR. WHERE DO I PLACE UN3481 STICKER

You place that sticker on an open area of the shipping box usually on the same side of the box as the shipping label. Sometimes the box may actually have a small or partial outline on the box suggesting where to place it. It just needs to be placed on the box and not be obstructed by anything else.

8730 wrote:

NONE

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what seems to be missing here—> How to send your Mac to Apple for service - Apple Support

Anywhere on the box. It's just a notice the box contains a battery.