Apple says owners should use Prepare to Ship before sending an activated iPhone 18 Pro Max. According to Apple's support page for the model, the iPhone 18 Pro Max has a battery capacity of more than 20 watt-hours, and devices with a single-cell battery over 20Wh face additional shipping requirements in most countries and regions. Apple handles that at the factory with a battery-and-firmware system that keeps capacity below 20Wh from manufacture through transport. Activating the phone lifts the temporary limit and makes the battery's full charging capacity available. It also hands the shipping obligation to the owner.
So if you've already activated an iPhone 18 Pro Max and need to send it somewhere — for a repair, trade-in, return, gift, private sale, or another purpose — Apple says to switch on a feature called Prepare to Ship first. MacRumors independently reported the same requirement on September 18, describing the firmware limit, its removal at activation, and the preparation owners now have to run themselves.
What Prepare to Ship actually does
The feature sits under Settings > General > Transfer or Reset iPhone > Prepare to Ship. Switch it on and the phone discharges its battery below 20Wh, then holds it there with a charge limit that stays in place during transit. You need a cellular or Wi-Fi connection. Apple says the discharge can take anywhere from a few minutes to a couple of hours depending on how charged the phone is when you start, and warns that the phone may become warmer than usual while it runs.
Apple says the process can take up to a couple of hours, so start it well before the handoff. If preparation does not finish or the phone does not show a ready-to-ship status, do not ship it; contact Apple or the receiving company because specific packaging may be required.
The 80% cap and the 14-day wait
One consequence outlasts the box. Prepare the phone for a repair, trade-in, or return and the feature caps charging at 80%, a cap you can only disable after 14 days. Prepare on the day you ship and the limit becomes removable two weeks later. Preparation selected for any other reason can be undone whenever you like. Apple also splits apart two steps people tend to treat as one: removing Activation Lock is mandatory when you return or trade in the phone, while erasing it is recommended but not required.
Who can skip it, and why this isn't a travel story
A new iPhone 18 Pro Max that has never been activated, still in the box or just out of it, is already held below 20Wh and doesn't need Prepare to Ship enabled. Apple says the process isn't required for other iPhone models, and neither Apple's page nor the MacRumors report extends it to the rest of the iPhone 18 lineup. It isn't an airport rule either. Apple says Prepare to Ship is not required merely to travel with the phone, and MacRumors reports the same distinction.
What Apple hasn't said
Apple's support page doesn't state the phone's exact capacity beyond saying it exceeds 20Wh.
If you're mailing one
Start Prepare to Ship well ahead of the hand-off, with Wi-Fi or cellular available, and confirm the ready-to-ship status before the phone goes in a box. For a repair, trade-in, or return, expect the 80% cap to follow the phone for 14 days. If you are returning or trading it in, clear Activation Lock before it leaves your hands. Then check your own return or send-back paperwork for the deadline that applies to you. That clock belongs to whoever you're shipping to, not to Apple's support page.