What to include
The imprint (Contact Page) should always contain:

Business name
Business address
Email address
Phone number
Add the following information if it applies to your business:

The name of your supervising authority, if your business requires a licence
Your license numbers or trade registry numbers
In the case of a legal person (corporate entity), you should state the legal form (full legal corporate name) and the authorised representative(s) of the business
Your VAT number
Your company registration number (or equivalent state-issued number)
The professional bodies of which you are a member
The names of the company’s directors