If a Norwegian tradesman works on his own home, he's supposed to pay VAT on the value of the work he's done - not only on the materials used.
I suspect such work is being under-reported, though.
Do you have a link here?
The obligation to pay tax only kicks in (as far as I can tell, IANAL) if the work is substantial and of a nature which requires professional skills.
Here's a recent link, though in Norwegian, I'm afraid:
https://www.fvn.no/abito/i/GM86x4/skatt-ved-arbeid-paa-egen-...
IANAL, and I have only heard about a couple of cases where people have been taxed under this statute - typically carpenters having built or renovated their own homes or cottages.
(Their obvious disadvantage being, of course, that the result of their labour is very tangible - and that whenever you do any significant building work, you'll need permits and documentation afterwards, making it difficult to discreetly renovate something off the books...)
Another thing that makes home construction a bit different in this regard is that you could claim to build a house for yourself, live in it for a bit, and then sell it on a couple of years later. That'd be an easy way to avoid or evade taxes. Not so easy with lettuce -- once you've eaten it, you've eaten it.