Example
We have issued an advance invoice for company XY for 150,000 CZK — the advance has been paid. Subsequently, we issued 2 final invoices: one for 120,000 CZK and another for 30,000 CZK. We now need to deduct the advance invoice partially from both final invoices.
Open the first invoice (120,000 CZK) and in the Items section, click the arrow next to the Add button and select Deduct Advance/Tax Document. In the following window, select the relevant advance invoice and the Deduction Amount table will appear. Enter the amount of 120,000 CZK here. The invoice will be zeroed out and marked as paid.
Do the same with the second invoice (30,000 CZK), where the Deduction Amount table will now only offer the unused remainder from the advance invoice, i.e., 30,000 CZK.