Local retailers have it easy when it comes to VAT. If you own a business in Belgium, store your goods in Belgium and sell to customers in Belgium, then you need to pay VAT to Belgium. End of story.
Online marketplaces like Amazon and eBay, however, complicate the story a thousandfold. These marketplaces are vast, dense networks of individual sellers, each of whom has their own obligation to pay VAT to the right tax authority.
Source: way2vat.com