For example, some cities did have laws taxing evert good entering their walls AND every good being sold there. In practice, only goods coming in through the port and sold at the market or in shops were checked. And for sales, in a world without automatic cash registers, how much you were due was pretty much left to the provost's imagination. Thus bourgeois would instead pay a fixed fee to the city to get a tax exemption. But you could also get exempted for many other reasons... and bluff that you were, because how the hell was the guard going to check.
But technically everything was taxed all the time."I come from a village exempted from taxes because a saint was born there two hundred years ago."
Roll Deception against a TN equal to a tenth of the value (in GP) of the items you sold today. If you pass, the guards let you go. If you don't...
Source: https://www.cairn.info/revue-le-moyen-a ... age-95.htm
