From 01.01.2002, corporate active clients of construction works in Germany have to effect a deduction of tax in the amount of 15 % of the invoice to be paid for a construction work, if a certificate of exemption for the constructor issued by the responsible revenue isn't available.

You can download here our certificate of exemption as PDF file.

On the web site of the Federal Central Tax Office you can check the certificate of exemption. More information to the withholding tax for construction works: Wikipedia (german).