Basically your profits are your income less expenses, and you only get taxed on your profits, so the higher your expenses, the lower your tax bill.
As a small business owner one of the most common expenses is your car, simply add up the miles you use for business, the cost of running the car, any payments you have made buying the car, insurance and compare it to the personal miles drove to come up with a business use percentage.
For example, if the total cost of running your car was £10,000 a year and 50% of the use of the car was for business, you could claim £5,000 as an expense. Now there are rules for leasing, buying, depreciating assets and different rules for vans but it’s probably best to discuss with an accountant
Paying expenses is simple, just make the expense, keep the receipt and at the end of the year, add them all up put this amount on your tax return. If you turned-over £50,000 and incurred expenses of £20,000 you will be taxed on £30,000 less any personal allowances.
As a small business owner anything you buy for your business is considered an allowable expense. This includes things like:
Cost of goods bought for resale (stock)
Cost of equipment you need buy
Advertising
Delivery charges
Heating and lighting in your business premises
Rent of your business premises
Postage
Stationery
Relevant books and magazines
Bank charges
Telephone use
Travel
Bank charges on business accounts
Also, its all here-
http://www.hmrc.gov.uk/incometax/relief-self-emp.htm
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