I'm curious to know what you think about this situation.
Approached an accountant firm to do two ordinary (ie full) tax returns. This involved a good bit of work, and they did the job fine.
A verbal discussion was held at the beginning stating the estimated amount of time for the work to be done, which was 10 hours. This stands legally as a tacit agreement.
The invoice arrives and - without any warning- 21 hours of work has been itemised. The cost of the invoice is unbelievable (nearly 6k), and the Swiss people who have looked at it (who include a CEO, finance director, and ex-fiduciary people) have laughed or said some unrepeatable things.
There is a legal obligation to inform if work exceeds the quoted estimate, which was not done.
Well if you have that in writing, there's no problem here whatsoever and you can even potentially get the bill down all the way to zero (or actual cost of 10h of their employee time, likely way lower than client quoted rate with a hefty profit margin) per Art 375 OR - they *had* to ask before overcommitting work else you gain the right to withdraw from the contract even after the fact.
If you don't have the stuff in writing, you have to tread very careful now with what you write to them. Try to get them to confirm the original estimate at least. Consider also what they have or will have in writing from you. If they have to sue you to get the money, the burden of proof is upon them - they get your money only if they prove you owe it to them. If it comes to "he says she says", the party burdened with proof (them) will in principle lose. But if they can prove at least that you agreed to work without a bound on hours that'll get tricky fast
What were they laughing at? The fact that you went to an accountant to do tax returns... You went to the top end of the profession for a job that is normally done by a technician (Treuhand)... From that point of view the fee is not surprising, but if you'd gone with the Treuhand, which is what people do, then I'd say it's about 5.5k too high.
Go to a lawyer, but this time make sure you know what you are signing up to and get a written estimate.
OP I would pay the portion of the bill you agree with when it's due
Then I would contest the rest and say you never agreed to the extra hours and that you wish to understand the details of a) what those are and b) why you were not informed as per law and quote article.
You knew the hourly rate which looks like about CHF 300 / Hour ?
It may just be that the full complexity of your tax affairs were not made clear at the time the initial estimate was made and I could easily guess that they hedged the estimate with vague statements. But they should have come back when it became clear that the there would be a significant deviation from the original estimate.
Anyway, you have now got template for your next tax return so you can better do it yourself.
A similar thing happened many years ago because I used an accountant to handle my UK tax affairs when I let a holiday cottage just after I moved here. I got what I considered to be an absurdly high accountancy bill. What caused the most outrage was, that on the tax form they submitted on my behalf, they entered an expense for accountancy services among the other deductions such as repairs, insurance etc. This accountancy expense was only a fraction of their bill. When I pointed this out they informed me that the Inland Revenue would never accept such a high amount for accountancy services.
They did other things which annoyed me. They took up contact with the letting agent and asked them a stack of questions, attempting to distinguish between repairs and improvements for rather trivial amounts. The agent didn't immediately answer and the accountant, on that basis, did not submit my tax form on time. The Inland Revenue apparently then issued some order which then had to be appealed against leaving me suspicious that the accountant had deliberately made affairs my more complicated than necessary.
Anyway, we agreed that I had ordered a proverbial Rolls Royce instead of a Mini and I did it myself from then on.
For an accounting practice 21 hours would not be unusual. There would probably be a partner and manager review as well as the accountant doing the work. Yes the quality is probably better and they are more likely to catch errors or missed expense claims, but you can afford a lot of mistakes before reaching 6k.
The OP picked the wrong type of service and then failed to get a written quote from the firm. Not going to be an easy one to argue.