You can delete an eBay account in the menu Setup » Markets » eBay » Accounts » Auth’n’Auth.

Important note before deleting

Note: End all active eBay listings before deleting an eBay account.

Delete account

1. Open the menu Setup » Markets » eBay » Accounts » Auth’n’Auth.
2. Click on Delete account (trash can icon) for the desired account.
3. A window with a security prompt will open.
4. Click OK to delete the account.

The account will then be deleted.