After an invoice has been created, you can make an adjustment on that invoice. Adjustments are amounts not limited to certain articles, and can be used for discounts, price adjustments etc
To make an adjustment, press the button called "Adjust amount". You will then be presented with a pop-up window.
Enter the article id, the amount to be adjusted, the description of the adjustment and the VAT in percent.
Please note that negative adjustments must be made with a "-" before the actual adjustment price and that a positive adjustment can only be made up to the original invoiced amount.
Also note that the text entered in the "Description" field will be shown on the invoice. To make the adjustment, press "Adjust amount". This will confirm the adjustment and it will be instantly processed.