Reset an Android Phone and remove it from your Google account
- Go to Settings > System.
- Tap Reset Options.
- Choose Erase all data (factory reset).
- Tap the Reset phone.
- Tap Erase everything. Your phone will be returned to the same state as when you purchased it.
Lastly, remove the device from your Google account. Head to the Recently Used Devices section in your Google account. Once you log in, you’ll be able to see which Android devices are connected and linked to your account. Find the phone you are selling, click on it, and then click Remove.