What about when they get it wrong?

HMRC recently screwed up on my partnership tax return, and demanded £100 from each of the three partners. I refrained from the middle-finger response, and after a surprisingly calm and reasonable correspondence, the charges were cancelled when someone at HMRC admitted fault.

What would have happened under these rules? They would have nicked the £300, no questions asked. And if I wasn't paying attention to my account, I might not have noticed at all. (A lot goes in and out.) It could well be the case that I would have never gotten my money back. I'll bet you anything it'd take a day for them to take the money, but 6 weeks to return it.