Thanks for your question.
Your first main expense is probably going to be materials - so you can claim what you have used to earn your income.
The next main expense may be motor expenses - there is a choice of two ways that you can claim these expenses, but note, whichever one you chose for this year, you have to stay with for the life of the vehicle you use.
The first way is the Mileage method. You add up all the business mileage you have undertaken and just multiply this by 40p - this takes into account the petrol, oil, repairs, MOT, Tax etc and also takes into account the depreciation on the vehicle itself.
The second method is the Actual Method - you must have kept details of all mileage, both private and business - to work out a percentage you can apportion to business use.
You then add up all the costs incurred on the vehicle - and apply that percentage against the costs, but you can also claim wear and tear on the vehicle as it then is also treated as a piece of business equipment - and you can claim capital allowances or the New Annual Investment Allowance - more about this further down.
Advertising - is allowable, as are all admin costs, like telephone & internet usage(if you email or have a website) postage, paper, ink for printer, envelopes etc etc
If you want more info on telephone and internet - let me know
If you use the internet then the computer also becomes a piece of business equipment, that you can claim under capital allowances or Annual Investment allowance.
REnt for any premises you pay out for - or maybe you work from home, and if you have a room in your home set aside as a workplace, then you can claim either £2 a week for every week your were self employed this tax year just passed, or apportion your heating and lighting costs. If you want to know more about this - just ask.
If you have a workshop - then again heating and lighting can be claimed -
Insurances you may have for your job are allowable, as are any professional subscriptions, or costs to be affiliated with any professional organizations.
Accountancy costs are allowable too - as are bank charges (if you have a separate bank account for business)
Wages paid to staff are allowable, but if this applies, be mindful if you pay anyone over £105 per week on a regular basis then you should register as an employer for tax purposes
Now onto business equipment that I suspect you use alot of.
If these items were previously privately owned and you brought them into the business, then you can claim capital allowances on them,. You add up the value of these items at the time you introduced them and can have 20% of their value for the tax year, deduct this 20% value from the total value, which them forms the balance value to carry forward for this tax year, At the end of this tax year, you then have 20% again of the value - and so on and so forth. (These can be apportioned if there is private and business use)
If however you have bought anything new for this self employment, then you can have a total of £50,000 of the cost (this is apportioned if you have been trading less than a full 12 months for 2008/1009) , so say you bought a saw and workbench, drills and spent £1500 this tax year gone, you can also have the full £1500 (this can be apportioned if there is private and business use)
This will be enough to get you sorted, but do come back and ask for anything else you need, and if you provide figures I will help you work out the amount you can claim.
Or if there is anything you have spent, that hasn't been covered, do ask if its allowable.