Is there a way to disconnect an old banking (checking) account that has remained as a duplicate account for the newly named and new quickbooks online banking account?

I'm here to help ensure you're able to make the account inactive, allaboutpoolsinc.

To avoid getting the error message, let's make sure the account is not used for your product and service items. Here's how:

1. Click the Gear icon at the upper-right corner and choose Products and Services.
   
2. From the Products and Services screen, click the gear icon above Action.
3. Select the Income, Expense, and Inventory account.
   
4. Locate the account in question from the list
5. Once you find the account, click Edit.
   
6. Change the account from there.
7. Hit Save and close.
   

Once done, let's go back to your chart of accounts and inactivate the account. We can take a look at the following article for the detailed steps in inactivating an account: Make an account inactive on your chart of accounts in QuickBooks Online. On the same link, we can find more information about what accounts can't be deleted.

This should get you moving today, allaboutpoolsinc. Don't hesitate to let me know if I can be of additional assistance. I'm always here to keep helping. Have a good one!