There is quite a lot of guidance on the tax office website here. Any tax owing will have to be settled out of his estate, which I assume is you. Similarly, his estate will get any rebate. And yes, you will have to file returns for April 11/12.
I would expect the accountant to sort everything out for a fixed fee (get it in writing) - although if receipts are in a mess you will probably have to find what you can so he has something to work with.
Everything Marion says is correct, but you don't have to wait to fill in the return for 11/12, you can do it all at the same time (you or the accountant will need to ask HMRC for a return for 11/12 as otherwise it wouldn't be sent until April 2012).
Feel free to CAT me if you need any specific help.
I dealt with my dad's affairs when he died, he was self employed and died without leaving a will. I got loads of help from a tax officer in his local tax office - I was surprised how helpful he was, he talked me through the forms sections by section and no question was too stupid. If you phone your local tax office they should be able to put you in contact with the officer responsible.
Likewise don't be alarmed if you start receiving letters about fines and interest penalties - in my case these were waived once all the paperwork was done.
the accountants are happy to help for a fee of £350 plus vat - what dh would normally pay them
but bugger me, if im paying them to fill in a few forms
i know what to do,as have filled in a few online as i have been se for my night nannying/ad hoc etc
but im good with keeping my receipts in order, unlike hubby so when i do it for myself its easy iyswim
he is def trading at a loss this year,as brought 2 vans as one had a very sore tummy and other van is being hoovered and sold as i type
im having trouble finding his bank accounts/statements (which have now been transfered to me) to find out how much tax he made from his money being in there, but again tbh it cant have been a lot knowing the banks interest rates
The accountant probably has some records relating to the previous van (assuming there was one before the 2 he bought?) that you will need. If there is a loss you can probably carry this back to 2009/10 and get a refund, but you will need to know the details of the 2009/10 return to confirm this. The claim for the two new vans will need to be treated as balancing charges as these are capital not trading expenses.
For £350 I'd jump at the offer to be honest (just make sure this covers all work up to and including a final return on cessation of business in 2011/12) - bear in mind this can be included in the trading loss and offset against previous profits.