I'm not disputing your statement, but it seems a bit unfair to me! We pay accountants for their expert advice, so how can we be responsible for ascertaining that advice is correct?
Your doctor doesn't ask you if you agree the medicine he prescribes is right for you before he gives it; an electrician wouldn't expect you to sign a waiver that you agree his work is correct etc.
The only part we should be responsible for is being truthful in the information we provide to them for them to prepare our accounts.
I agree with you Ian, completely. I'm pretty sure though (almost certain) that even still, the responsibility falls back to you. I think the stance is- you employ them, it's your risk if they are filed incorrectly!
Remember, this is the HMRC, normal rules & regulations do not apply. In a court of law, the defendant has to be proven guilty (beyond reasonable doubt) before judge & jury. With your tax affairs & HMRC YOU have to PROVE YOURSELF not guilty, HMRC will make assumptions & these assumptions will be treated as correct unless you prove otherwise, all at your expense too!!
Insurance would be a lifesaver in these circumstances, even if you couldn't prove everything (it's almost impossible when you get right down to the nitty gritty) they can play an important role in reducing any penalty you may be lumbered with.