The new phone is working, so the old one goes into its box for sale. Before it leaves, consider what it can still open: camera views, alarm controls, door access and the email account used to recover those services. Moving a SIM or installing the apps on a new handset does not by itself prove every old session has ended.
Start with the new phone. Confirm that you can sign in through the official apps, complete verification and reach the equipment you are authorized to use. Check the notification settings you rely on. This is a good moment to discover a missing recovery method, while the old phone is still under your control.
Review the accounts, not only the icons
Use each service's account or device-management controls to review signed-in devices and authorized sessions where those features exist. Remove the old phone through the supported process. Deleting an app icon is not necessarily equivalent to revoking a session on the service.
If the phone holds an authenticator, passkey or another sign-in method, follow that provider's transfer instructions. Google lists several recovery options for two-step verification, but availability depends on what was set up for the account. Do not erase the only working verification method and assume the same phone number will solve every recovery problem.
Check locally stored information too. Downloaded camera clips may be in the photo library or file storage rather than inside the security app. Preserve anything you need in an appropriate secure location before preparing the handset for sale. Avoid sending private footage to a broad shared folder simply to get it off the old phone quickly.
Follow the phone manufacturer's current steps for signing out and erasing the handset before transfer. Deal with its device-lock and ownership features as instructed so the next owner can legitimately set it up. If it contains a removable memory card or SIM that should stay with you, handle those separately.
Check the new routine afterward
Once the old sessions are removed, verify normal access from the new phone again. Review a fresh recording, receive a test notification through an appropriate non-emergency event and confirm that your recovery options are current. For a household system, make sure another authorized person still has the access they are supposed to retain.
If the old phone is lost rather than being sold, use the account and phone provider's lost-device procedures promptly. That is a different situation from a controlled handover and may include remote sign-out or credential changes. In either case, the useful question is not whether the old phone looks empty. It is whether the accounts and data have been deliberately moved out of its reach.
