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Is it legal to sell food on the streets of Brussels? (from a cart)
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The English part is incomplete but then if you want to do business here...
Seriously, lots of hoops to go through. For a start, how is your friend going to register their business so they can pay tax? Then there is is the food hygiene certificate to be gained. Then you have to be cleared by the commune to be there.
There may be more than this to do too. Registering the business is just a start.
So there's at least one gourmet food truck in brussels: http://www.keepontoasting.be but there are all those gaufre and ice-cream trucks. Do they have an association?
I've seen the odd snails truck.