When a German company sends an invoice to another EU member state, it is responsible for checking the correctness of VAT number and company details. (information in German). One of the ways to check the validity of a VAT number and to request a confirmation letter, is to use the site of the Bundeszentralamt für Steurn.
The "USt-IdNr. Bestätigung"-panel in the invoice detail page of System One is integrated with the API of the Bundeszentralamt für Steurn to offer an efficient way to check data and request a confirmation letter.
Data isn't matching
The combination of VAT number + Company name + City name is checked. When information is not matching, you are notified and you should correct the company information in System One before you can continue.
To find out the correct information, you could ask your customer, or look up the information by VAT number in the online VIES interface.