Instead of resetting the user's password and changing its mobile number, you can delete their access since they already resigned. This way, they can no longer access the company file. Here's how:
Sign in to your QBO account as the master admin.
Click the Gear icon, then select Manage users.
Find the user who resigned. Then, click the arrow down icon and choose Delete.
Click Delete again to confirm.
I'm adding this article for more guidance: Delete a user.
Just in case you want to know what your user's entering or doing, you can run the Audit log report. It allows you to verify who's users made changes to your books and what they did.
I'm still open to your replies if you need further assistance managing users. Have a great day ahead!
It's sad to hear your employee is gone. I hope everything is well, and I'm here to provide you some information about resetting a user's password. I'll make sure you'll be able to access the account using the employee's email.
You can use the user's email by resetting the password. Make sure you'll be able to log in to your QuickBooks Online account.