I do not have an accountant. One could probably save you money, but these days you can most information from Customs & Excise on line or the phone.
Basically your equipment inc van costs, you enter into a Capital Expenditure Pool.
For these purchases in the year beginning 1st April 2009 to April 1st 2010 you can claim 100% against tax due as an Investment Allowance, up to £50,000.
Normal writing down allowance is now 20% which will reduce to 18% in 2012.
If your income does not cover your personal allowance, there is no point in claiming any Investment or first year allowance or any writing down allowance.
These Capital costs then stay in your Capital Expenditure Pool and you can claim the normal 20% (or 18% as it will soon be) in later years.
For example.
Van cost £5,000
Equipment £4,000
Total £9,000
Less private use of van (Say 10%) - £ 500
New Total £8,500 this goes into your pool.
Not making any Capital Allowance claim this year means you can claim a maximum of £8,500 x 20% = £1,700 capital Allowance
the following year, leaving £8,500 - £1,700 = £6,800 to carry forward to year after.
Don't forget you have to deduct the same percentage of personal use of the van against all your other van costs - fuel, insurance, mot, service, excise license and repairs etc.
Some guys use a mileage allowance scheme, which allows you to claim so much per mile your van has covered in the year. This makes it easier as you dont have to calculate all the expenses together. However using this scheme, you do not also claim for the expenses already mentioned, i.e. furl etc. You use the mileage allowance scheme or the full expenses scheme, one or the other, not both. You have to decide which one to use when your van is first introduced into the business as you cannot change the scheme until you get a different van.
One thing to be careful about is that if using the Mileage Allowance scheme - You cannot claim ANY Capital Allowance on your van, as this is automatically allowed for in the Mileage Allowance.
I know its all a bit to take in at first, but it's quite simple really, hope this helps.
Dave.