Juli Clover:

The iPhone 18 Pro Max has a battery capacity over 20 watt-hours, which means there are additional shipping requirements. If an iPhone 18 Pro Max needs to be shipped somewhere, its maximum battery capacity has to be limited through firmware.

[…]

Customers who need to ship the iPhone 18 Pro Max for repair, trade-in, or other purposes have to use a new Prepare to Ship feature. Prepare to Ship discharges the battery to below 20Wh and sets a charge limit so the iPhone stays below the threshold during the shipping process.

Laptops, of course, have larger batteries, but they aren’t affected because each cell is below the limit.

Battery Life iOS iOS 27 iPhone 18 Pro Max Legal