What form does the certification of place of business require? Is a business card with an address sufficient, or does it have to be a signed document?

The certification of place of business should take the form of a signed letter from your employer certifying that you are employed by that company, as well as the capacity in which you are employed and the address at which you carry out your duties. The letter should be signed by either a professional representative, a member of the HR department of the company, or a person entitled by law to sign on behalf of the company (chairman, managing director etc.). A business card is not sufficient.