Erase your device
If your iOS device or Mac is lost or stolen, you can erase it if you set up Find My iPhone on the device before it was lost.
Important: Before you erase your device, try to locate it or play a sound on it. After you erase it, you can’t use Find My iPhone to do either. You may still be able to locate your Mac after you erase it.
Erase the info on your lost device
Sign in to Apple ID (the one you use with iCloud), then click Find My iPhone.
If you’re using another iCloud app, click the app’s name at the top of the iCloud.com window, then click Find My iPhone.
Click All Devices, then select the device you want to erase.
In the device’s Info window, click Erase [device].
An iOS device: Enter your Apple ID password. If the device you’re erasing has iOS 7 or later, enter a phone number and message. The number and message will be displayed on the screen after the device is erased.
A Mac: Enter your Apple ID password, enter a passcode to lock the Mac (you’ll need to use the passcode to unlock it), then enter a message. The message will be displayed on the screen after the Mac is erased.
If your device is online, the remote erase begins. A confirmation email is sent to your Apple ID email address.
If your device is offline, the remote erase begins the next time it’s online.
If you erase then find your iOS device, you can restore the information on the device using iCloud Backup (if backup was turned on before you erased it) or iTunes. For more information, see iCloud storage and backup overview, or your device’s user guide in Safari bookmarks or on the Apple Support website.
If you erase then find your Mac, you can restore the information on the Mac using a Time Machine backup. For more information, see the Apple Support article Recover your entire system. If you set an EFI firmware password on your Mac before it was lost, then erase it and later find it, you may need to take your Mac to an authorized repair center to unlock it before you can use it again.
Note: If you don’t expect to find your iPhone or iPad (Wi-Fi + cellular models), you should contact your wireless service provider to suspend service so you aren’t responsible for phone calls or other charges.