In Order Time there is a place to add an account however QBO discount box does not actually use accounts whereas QuickBook desktop does.
We are actively seeking a permanent solution however you can work around this issue as follows.
- Create an Item call Discount using the Other Charge Group
- Make sure to select the correct Income account.
- Add the item to a sales order with quantity of 1 but a negative price.
Upon syncing to QB, the Income account associated with the Discount item will be DEBITED.