I have been on a course which the Inland Revenue offer and run.
Its totally free and takes about 5 hours, telephone your local tax office or go to their web page for more details.
I would recomend this even if you are using a accountant, because the less work a accountant does the less you pay.
What is tax deductable and what is not and how much you can claim is quite simple.
If you have had to spend money to run your business, then this is tax allowable, if you already spend this even without a business then its not allowable. For example you rent you home and run your business from there, bacause you would have to live there anyway the rent is not allowable but other household expenses are.
Any capital expense over £200 like equipment-vechicles-computers you can claim 50% in the 1st year then 25% per year thereafter until you have claimed the total cost back, if you see the item then this figuure must be taken away from the cost and the rest is what you can claim for, if you make a profit on something you sell then you have to pay tax on this profit.
If you lease a vechicle or equipment then you can claim 100%.
You can claim for the use of a room in you home, if you can prove that its only used for the business, so if you use a bedroom, there must not be any type of bedroom furniture in it, you can only claim a percentage of your Council Tax - Gas - Electric, you cannot claim for rent or mortgage because you would have had to pay for this even if you werent in business.
The percentage you can claim is as follows, you count the total rooms in you house but not the kitchen bathroom or hallways, so if you live in a 3 bedrrom house with 1 livingroom and use 1 bedroom for business you can claim 25%.
If you use only part of the livingroom or garage then you can only claim a nominal amount of £2.00 per week.
If you use your home phone then you will have to show the call costs you have used for the business, you cannot claim for line rental unless the phone is only used for the business.
You can claim for working clothes but you cannot claim for suits and smart dress.
You can claim for gifts to your customers so long as its only £50.00 per customer per year.
You cannot claim for business lunches or drinks, but you can claim for hotel and food if you are away on business. (proof will be required)
It is worthwhile to have an accountant as the tax rules change every year and they will save you more than their costs in most cases.
It is also worthwhile to join the Ferderation of Small Businesses because they offer an insurance policy as part of their membership that covers your cost if you have a tax investigation, which can be very very expensive.
Remember to kept every bill-every bank statement-every weekly income sheet, you will need to kept this information for 6 years, so look after it like gold.