QuickBooks Online uses Income Accounts to categorize the cash inflow of your business.The balance in the appropriate income account appreciates by the value of the product(s) sold each time a new invoice or sales receipt is created. Under Inventory Settings, select the account from the drop-down menu for accounting income for the products.
Note: This account is used only while creating new Products. You can freely change the Income Account manually. After creation, the Product account cannot be updated.