Term used in the German VAT Act (§ 18 UStG). Business owners must file monthly, quarterly, or annual advance VAT returns to report the transactions carried out and to pay the respective VAT to the tax office. Both the VAT achieved through sales or services and that paid on purchases for the company (input tax) are reported. Only the difference between VAT and input tax (tax payable) is paid to the tax office. Payments made previously, including any advance payments made, are credited in the final VAT return.

Source: UStG, edited (only available in German)