Let me be the first to welcome you to the Community. I can provide some information on removing an accountant in QuickBooks Online (QBO).
You can remove the current accountant from your company file by going to the Manage Users section. However, you must be logged in as the Master or Company Admin to execute this action. Let's make sure you have Admin rights to process your request in removing an accountant user.
Go to the Gear icon and select Manage Users.
From the Accounting firms tab, find the accountant you want to remove.
Select the small arrow dropdown in the Action column and tap Delete.