Transfer your mobile service, authenticator codes and passkeys before erasing personal data—and verify that the replacement phone can actually sign you in.
Key Takeaways
- Back up and transfer your data before disconnecting accounts or resetting the old phone.
- Move cellular service, authenticator codes and passkeys, then test them on the replacement device.
- Remove Google Accounts from Android or follow Apple’s sign-out and erasure process before handover.
- Use the built-in factory reset; deleting individual files is not an adequate substitute.
- Deleting an eSIM profile does not necessarily cancel the associated cellular plan.
A factory reset should be the final step when selling, trading in or donating a phone—not the first. Before surrendering the device, confirm that your data, mobile service and account-verification methods work somewhere else. Otherwise, a properly erased phone can still leave you locked out of important accounts.
Before you begin: Keep the old phone connected
Do not erase the old phone as soon as the replacement turns on. Keep both devices available, charged and connected while you transfer information and test access. Some authenticator migrations require the old phone, and account changes may involve security checks or delays.
Apple notes that Stolen Device Protection can impose a one-hour delay on certain account changes. Menu names may also differ across iOS releases, Android versions and phone manufacturers, so check the linked official instructions if the options on your screen do not match this checklist.
1. Back up and transfer your personal data
- Create a current backup. Both Apple and Google direct users to back up before resetting an old phone.
- Transfer the information you intend to keep. Confirm that contacts, messages, photographs and other necessary content appear on the replacement device or in the relevant backup.
- Inventory your accounts and login methods. The UK National Cyber Security Centre recommends checking account details and confirming that services such as smart-home controls remain accessible elsewhere.
- Do not manually delete synced iCloud content as a cleanup method. Apple warns that manually removing synced information can also delete it from iCloud and connected devices. Use Apple’s documented erase process after the transfer is complete.
2. Move your SIM or eSIM service
Make sure your phone number and cellular service work on the replacement phone before erasing the old one. A carrier may need to transfer or cancel service, depending on the account and device.
If you are selling an iPhone with an eSIM, Apple says to choose the option that erases both the device and its eSIM profile during the documented erasure process. Deleting an eSIM profile does not, by itself, cancel the cellular plan, so contact the carrier if cancellation or another account change is required.
Remove any physical SIM or memory card where applicable. For non-Apple eSIM devices, follow the phone manufacturer’s and carrier’s current instructions rather than assuming that deleting a profile ends the plan.
3. Transfer authenticator codes—and test them
An authenticator app appearing on the new phone does not always mean every account is ready for use. Test account verification on the replacement device while the old phone is still available.
Google Authenticator
Google Authenticator can synchronize codes through a signed-in Google Account. If you use the app without an account, transfer the entries manually: export them as one or more QR codes on the old phone and scan those codes with the new phone. Wait for the new device to confirm completion, then test the transferred codes.
Do not start deleting synchronized entries from the old app merely to tidy it. Google warns that deleting a synchronized code can remove it from every synchronized device. Current synchronization and transfer behavior also depends on the app version and whether it is signed in to a Google Account.
Microsoft Authenticator
Microsoft supports cloud backup, but restoration works only between devices of the same platform type. An iOS backup cannot be restored to Android, or vice versa. On iOS, the backup also depends on the relevant iCloud services being enabled.
Restoration varies by account. Standard one-time-password accounts may recover their codes, while passwordless Microsoft accounts and work or school accounts may restore only the account name and require another sign-in. A visible account entry is therefore not proof that verification is operational.
Microsoft says its Android backup system is scheduled to change in January 2027. Check Microsoft’s current support page if you are transferring near or after that date.
4. Review passkeys and keep another way to sign in
Passkeys require a separate review because they may be stored on the phone, synchronized through a platform or held by a third-party credential manager. Confirm that the replacement device can use the required passkeys, and retain another working sign-in method before giving up the old phone.
For Google Accounts, review the account’s passkeys and device sessions. Google says manually created passkeys may need to be removed separately, while signing out a device session removes automatically created Android passkeys. Also inspect any third-party credential manager you use.
Do not rely on a newly created Google passkey as your only immediate route back into the account. Google says a new passkey may take up to seven days to become available at sign-in. It also warns that an existing Android passkey may remain usable for up to six hours after the device is signed out.
These details apply to Google Account passkeys. Passkeys managed by Apple, Microsoft or another credential provider should be reviewed using that provider’s current documentation.
5. Run a no-lockout test on the replacement phone
Before resetting anything, verify the full sign-in process rather than checking only that apps and account names are visible.
- Test cellular service. Confirm that the transferred number and plan operate on the new phone.
- Open transferred data. Check that the information you need is present and usable.
- Sign in to key accounts. Confirm that passwords or passkeys work.
- Complete verification prompts. Test authenticator codes on the replacement device.
- Check connected services. Confirm that controls needed for smart-home systems or other linked services remain available elsewhere.
- Preserve a fallback. Keep another functioning sign-in method until the transition has been fully tested.
6. Disconnect accounts before the factory reset
For an iPhone
Apple instructs sellers to sign out of Apple services and then use Erase All Content and Settings. Following the documented process turns off Find My and Activation Lock. Afterward, remove the old phone from the list of trusted devices.
If you are moving to a non-Apple phone, Apple also directs you to deregister iMessage. During erasure of an iPhone being sold with an eSIM, select the option to erase the device and eSIM profile.
For an Android phone
Google’s documented sequence is to back up the phone, open the account settings, remove every Google Account and then use the system’s Erase all data or factory-reset option. Removing the accounts before the reset separates them from the device before ownership changes.
Exact paths vary by Android version and manufacturer, but Google describes the relevant areas as Passwords & accounts and System > Reset options. Check the phone maker’s current instructions if those labels do not appear.
7. Use the built-in erase function
Do not prepare a phone for sale by deleting photographs, messages and apps one at a time. The NCSC recommends using the built-in Erase All Content and Settings or Factory Reset feature. Do not select an option that retains personal files.
A reset is intended to remove personal material such as messages, contacts, photographs, browsing history, Wi-Fi credentials, passwords and installed apps. People with unusually high-security requirements should consult specialist secure-sanitization guidance, as the NCSC notes that a determined specialist may potentially recover data.
Final handover checklist
- Your current backup is complete.
- Required data opens on the replacement phone.
- Cellular service works on the replacement device.
- Authenticator codes have been transferred and tested.
- Passkeys and fallback sign-in methods have been reviewed.
- Smart-home and other linked controls remain accessible.
- Google or Apple accounts have been disconnected as directed.
- Find My and Activation Lock have been removed from the iPhone through Apple’s documented process.
- Physical SIM and memory cards have been removed where applicable.
- The built-in factory-reset process has completed without retaining personal files.
- The old device has been removed from trusted-device or account lists where required.
What This Means
The safest order is transfer, test, disconnect and erase. Backing up protects your files, but it does not prove that your eSIM, authenticator codes or passkeys will work on another device. Complete a real sign-in and verification test before the factory reset. Once every necessary service works elsewhere, remove the old phone from your accounts and use its built-in erasure process.
Sources
- Apple Support — What to do before you sell, give away, or trade in your iPhone or iPad
- Google Account Help — Reset your old Android device
- Google Account Help — Get verification codes with Google Authenticator
- Microsoft Support — Back up your accounts in Microsoft Authenticator
- Google Account Help — Sign in with a passkey instead of a password
- UK National Cyber Security Centre — Buying, selling and donating second-hand devices
