If you are a VAT registered publisher according to German UstG (German VAT Act), you are liable to pay VAT to the German tax authorities. Make sure you provide all tax-relevant information so that zanox can include VAT on your credit notes. It is your responsibility to pay the VAT declared on your credit notes to your local tax office.
NOTE: zanox assumes no liability for your tax affairs. Please consult your tax consultant or local tax office to make sure you are legally compliant.