Change of rules & regulations after accepting faculty contract offer I have recently accepted a new academic position in the Netherlands. Netherlands has a generous so-called 30% rule for high skilled expats:

you are paying taxes only for the 70% of your income and the rest 30%
is given to you as a tax-free allowance. This, in practice, means
about 20% higher net salary.

I easily got this rule 2 years ago for another academic position again in NL. The duration for the 30% rule is 8 years so I should have it for the next 6 years and nobody from HR mentioned any plans from the government of reducing it. Unfortunately, yesterday I read in the news that Dutch government completed a draft proposal which reduces the 30% rule from 8 to 5 years.  What is worth noting is that, in case the draft becomes a law (which most probably will, since this is the final proposal) will have a retroactive effect :

Concreet betekent dit dat het kabinet in het pakket Belastingplan 2019
zal voorstellen de maximale looptijd van de 30%-regeling met ingang
van 1 januari 2019 voor zowel nieuwe als bestaande gevallen met drie
jaar te verkorten.​

One of the factors that made me accepted the new offer was the 30% rule for the remaining 6 years (I planned to buy house immediately). Now I see that this might not very well be true. What is even worse is that I turned down a great Research position (in a high tech company) offering about 60% more salary. I thought the 30% rule would partly compensate about it, but probably it will not.
I will not ask about the legal aspects of the draft law nor about the ethical dimension of this although you can see here what the relevant tax authorities say about shortening the period of 8 years.

Is it too late to turn down the academic offer? I have accepted it on e-mail but I haven't signed anything yet and haven't even seen the contract. If yes, what is the best way to do this?
Is anything similar happening to any other country and how do academics people deal with it?

Apparently, a lot of expats taking advantage of this rule get frustrated and set up an e-vote against the draft.
This is an unfortunate situation were nobody really is to blame. You can't expect the university to warn you about a law that wasn't even in place yet, and the university cannot objectively be mad at you for reneging when your contractual situation significantly changed, even if it is due to outside factors. Of course the important word in the above statement is "objectively" - nobody can ensure you that the people that wanted to hire you will also see it like that, and that you won't burn any bridges.


  Is it too late to turn down the academic offer? I have accepted it on e-mail but I haven't signed anything yet and haven't even seen the contract. If yes, what is the best way to do this?


As long as you have not signed anything you are always in the right to back out. The best way to do it would be to warn them that this new development significantly changes your view on their offer, even if they are of course not to blame. I would stay clear of any accusations that they failed to inform you in advance. Note that this also gives them the option to up their offer, which would presumably change your mind back again.

You should do it in the same form as you tentatively accepted the offer before - if you communicated that you would take the offer via email, send them a brief follow-up that you changed your mind, and why.


  Is anything similar happening to any other country and how do academics people deal with it?


I am not aware of any concrete cases, but presumably when Brexit broke there had to be cases of academics changing their mind about moving to the UK.