Example: a friend of mine makes artisanal chocolates. When he started out he didn't have a licensed kitchen, any kind of food/health license, or sales tax collection. Nobody cared. Why? Because he got compliant before his company grew enough to be on anyone's radar.
Here in the US you can launch first and worry about legal compliance later.*
*Not for all industries or all definitions of "later".
But I know one person who has done his own accounts (small company, 3 people I think, accounts included VAT and payroll) and he didn't seem to think it was too bothersome. The documentation provided by the UK tax authorities is actually generally pretty good. But the punchline to his story was that when he eventually hired an accountant, mainly to save time, it turned out he'd missed a number of opportunities to take advantage of this or that way of reducing tax payments. So it seems like the DIY approach might not get you in hot water, but a lack of relevant training and experience could still prove costly.
Based on this story I signed up for an accountant from day 1 ;)
The UK has the NIH though; maybe in 10 years the Obamacare/Switzerland-Lite model will prove itself superior to the NIH, but it's not there yet.
I don't know of UK taxes specifically, but US taxes are a nightmare compared to every other tax regimes I am familiar with (a couple of European ones).
The 20% VAT you mentioned earlier seems onerous, but when you factor everything, taxes in the US are often as high or higher than other places, and provide significantly less:
e.g. suppose you are living in NYC and earning well. Then you pay %35 federal (or is it %39 yet), + 8% state + 5% city on income, for a total of %48 income taxes. If you are an employee, you have to add SS, employment tax, fica and whatnot on top of that, which easily gets you past the 50% mark. But that doesn't actually include any kind of health coverage, and when you go to university (or your kid does), you're going to pay 5-10 times as much. To an american, it seems reasonable to borrow $200K at age 20 against your future earnings to go to college, even though 40% don't get to the finish line (student loans, so not even dischargable by bankruptcy). It would be considered insanity, if it was even a possibility, everywhere else.
Oh, and you still have the 8.5% tax in NYC. not 20% VAT, but not that far - and the VAT is not as simple as it looks - if you run a business, it often doesn't affect you as much, because in many countries, only the "last mile" pays it.
Finally - US tax law regarding domestic finances might be comparable to the UK one (I would guess not, with the US federal code standing at >70,000 printed pages, and IIRC the UK code standing at <20,000). But if you have another nationality, or a significant investor of yours does, or you have anything resembling a bank account outside the US - then US tax laws become ten times more complex, and you are assumed guilty at any point of the way. (Failed to file your FBAR? Pay 50% of the highest amount in your account. Per year of missed reporting).
If you lived in Austin Texas you'd avoid that 8% state tax and 5% city tax.
Most major (and minor) US cities do not have an income tax. And a few states don't even have an Income tax (Texas, Alaska, Florida, Nevada, South Dakota, Washington and Wyoming). You could probably include Tennesse And New Hampshire in there too as they only require tax on dividends.
The reason why NYC and NY State can get away with charging those tax rates is that there's a sizable contingent of people who can't imagine living (or working) anywhere else other than NYC (it's a hell of a city). When you have a captive tax base like that it's in the state's rational best interest to jack the rates up as high as possible.
My advice: Vote with your feet.
Is this the case?
(I admit that 'ease of compliance' and 'tax code being complicated' are not the same)
I think businesses under a certain revenue threshold, though, are exempt from calculating destination-based VAT, so it doesn't hit small businesses.
For reference, the threshold for Denmark is about 38k Euros, so you (the UK-based bookseller) wouldn't deal with this until your sales _to Denmark_ topped that amount annually.