Tax, made real

Dick Puddlecote has the right idea on how to introduce his kids to the concept of taxation:

I'm not sure exactly when the practice started, but we've taken to pinching small portions of the little uns' bits and bobs every now and then. For example, a few chips from a Maccy D's meal, a spoonful of their after dinner dessert, a couple of sour sweets from the pick'n'mix. You know, that sort of thing.
We call it 'tax'.
[...]
They each received a Galaxy selection box, amongst other things, yesterday morning and we - with tongues firmly in cheek - announced that the tax would be a Ripple bar from one and a bag of Minstrels from the other. It was heartening to find out later that the very sweets in question had, without our noticing, been spirited away into hiding places in their rooms.

Is this tax avoidance or tax evasion? Whichever, the parents have been deprived of illegitimately acquired cavities.