Hello there, Steve. You'll need to remove the old user and add the new one. I'm here to guide you through the steps.

Since the user is no longer with the company, it's best to delete their account to avoid any confusion:

1. Go to the Gear icon and select Manage users.
2. Navigate to the user and click the Edit dropdown.
3. Choose Delete.

Then, add the new user:

1. On the Manage users page, click the Add user button.
2. Fill in the necessary details.
3. Select the same role and make the changes you want.
4. Once done, click Send invite.

For more details, please refer to the article: Add and manage users in QuickBooks Online and Intuit Enterprise Suite.

Moreover, to enhance your QuickBooks experience, consider collaborating with our QuickBooks Live Expert Assisted team. These financial professionals specialize in streamlining processes and providing tailored advice to meet your business's unique needs.

Additionally, you can check the audit log to see changes made in your company.

Please return to this thread if you have other questions about assigning users to your company in QBO, Steve. We're here to help you in any way we can.