With the certificate 22f UStG, the tax authorities confirm to the applicant that he is duly registered for tax purposes. Electronic marketplaces such as Amazon and eBay require their traders to have the 22f UStG certificate. The tax authorities check whether the electronic marketplaces can present their traders' certificates. If these cannot be presented, the electronic marketplaces are liable for the tax that the traders must register, declare and pay. Since the electronic marketplaces do not wish to assume liability, they will not allow traders without certificates to do business on their marketplaces.