Cant book invoice due to lack of a booking key.

Error when Invoice is approved and booked: "Error The bookingkey for the tax 19 % Umsatzsteuer EU Lieferung is not configured!"

Under Finance->Configuration->Sales Tax the booking key for all taxes is "-1" How to find, install, add the booking keys? Found the reason myself. Missing DATEV Booking Keys due to installation of the Datev connector. In Datev SKR03 für USt. 19% = 13. I added it by hand.

Thanks in Advance.