The transfer copies your data across, but it leaves two jobs to you. First, check that you can access all your accounts on the new device and use them without the old phone. Second, reset the old device completely before passing it on, so the next owner can use it without getting any of your personal data.

First: take your digital keys with you

A banking app may look familiar on your new phone but still not let you authorize transactions. Transaction approval may be deliberately tied to a single device. Authenticator apps, which generate additional sign-in codes, may also need to be transferred separately, depending on the app. Passkeys – digital sign-in keys that replace passwords – can be synced or tied to a specific device. Your password manager’s vault must also be available on the new device, and you must be able to unlock it.

Before erasing the old phone, create an up-to-date backup and check the photos, contacts and local files that were transferred. Remember your chat history too: a messaging app such as WhatsApp may require a separate transfer or need to be restored from a backup. Follow each service’s instructions for switching to a new device while the old phone still works. Store any recovery codes you are given somewhere other than on the phone. You must also know your Apple or Google account password, even without the old phone.

Then switch off the old smartphone as a test. On the new device, unlock your password manager and sign in to important services again – also testing an authenticator code or passkey if you use them. For banking, checking your balance is not enough: test the approval process on a transaction you need to make anyway. What matters is not a “Backup successful” message, but being able to access your accounts without the old phone. If you still need to confirm anything on the old smartphone, the move is not complete – do not erase it yet.

The cloud deletion trap: do not clear things out manually

After these checks, it may be tempting to delete the old photos and contacts one by one. Do not do this if they are synced: those items may also be deleted from the cloud and from every connected device. The pictures you just transferred could therefore disappear from the new phone as well. Deleting individual files is no substitute for a factory reset anyway.

A full reset is different: it removes the content stored on the phone without emptying your cloud library. That is by design, because your cloud library is meant to stay intact when you change devices.

For the next owner: unlink the phone from your accounts

Now turn the old phone back on so you can unlink it from your accounts. This means signing out on this device, not deleting your Apple or Google account. If a bank or another service still has the old phone registered for approvals, remove it there too.

On an iPhone, Activation Lock prevents someone else from setting up a device linked to your account. Erasing it completely through Settings turns off “Find My” and Activation Lock. This requires your Apple Account password, unless the device was already unlinked when you signed out. Simply removing apps or resetting individual settings is not enough. If the lock remains, the next owner cannot activate the device.

After an Android phone is reset through the recovery menu – accessed using the device’s physical buttons – or erased remotely, Factory Reset Protection (FRP) may require the previously linked Google account during setup. FRP normally does not apply to a standard reset through Settings that you confirm on the device itself. Even so, remove your accounts from the device before resetting it. Also sign out of any Samsung, Xiaomi or other manufacturer account, as these accounts can have their own locks.

Factory reset: once is enough

On modern smartphones, this standard factory reset is enough to erase your data. iPhones and current Android devices encrypt their internal storage by default. During a reset, the necessary decryption keys are discarded, ensuring that any data left behind cannot be read. You do not need to overwrite the phone seven times or fill it with dummy files.

You cannot assume the same is true of very old, unencrypted devices. For those devices, check the manufacturer’s guidance on secure erasure. If you are still unsure, professional disposal that includes data destruction is safer than passing the device on.

Do not forget the SIM, eSIM and memory card

Before resetting, check that calls and SMS work on the new phone. The order matters: depending on your provider, you may have to request the eSIM profile again rather than simply transferring it. Do not delete it until you can make calls on the new phone. Then remove the physical SIM from the old device. Also delete the eSIM profiles – the mobile network credentials stored on the embedded SIM. When erasing an iPhone, choose the option to erase both the device and the eSIM profile; on Android, make sure the profiles are erased too. Handle a microSD memory card separately – the easiest option is to keep it. Important: deleting an eSIM profile does not cancel your phone contract.

iPhone: sign out and erase

First, unpair any Apple Watch that is paired with the phone.

1. Settings > [your name] > Sign Out. Follow the confirmation prompts and have your Apple Account password ready.

2. Settings > General > Transfer or Reset iPhone > Erase All Content and Settings. Confirm that you want to erase everything, including any eSIM profiles.

If you are switching from iPhone to Android, you should also deregister your phone number from iMessage. Otherwise, messages from iPhone users may not reach your new phone because they are still being sent via iMessage. This can also be done later through Apple’s website, without needing an iPhone.

Android: the standard method

1. Remove your Google account and any Samsung, Xiaomi or other manufacturer account from the device.

2. Then start the factory reset through Settings, not through a recovery menu accessed using the device’s physical buttons. The exact menu label depends on the device; confirm the reset with your PIN, pattern or password.

The final check before handing it over

After the reset, the device should start up with the setup screen, not your previous home screen. But that alone does not prove the account lock is gone. Connect the phone to the internet and follow the setup steps past activation. If you can continue without your previous account details and the phone does not ask for a previously linked account, the lock has been removed – simply switch the device off again. Do not add an account of your own. You can also carry out this check yourself before shipping the phone. For an iPhone, also remove any remaining entry for it from your list of trusted devices.

Your checklist, in order:

1. Back up your data and chats, then check them on the new device.
2. Test banking, approvals, authenticator apps, your password manager and passkeys without the old phone.
3. Remove the old phone as an authorized device for transaction approvals and sign it out of your accounts; on Android, remove the accounts (Google and any manufacturer account) before resetting.
4. Remove the SIM and memory card, then fully reset the device through Settings – erasing the eSIM profiles too.
5. Check that the setup screen appears and the device is no longer linked to your accounts; only then hand it over.

Have you ever been stuck after switching phones because you could no longer authorize transactions or ran into an activation lock? Share your experiences in the comments.