These are all the ongoing expenses associated with running your business that you can deduct from your 'gross profit' figure on your profit and loss account to calculate a figure of 'profit before taxation'.
Legitimate business expenses for accounting purposes are:
Note that some elements of these expenses are not allowed for tax purposes and are added back before your taxable profit is calculated.
Where expenses apply partly to business and partly to non-business or personal use, you need to exclude any expenditure that relates to non-business use. For example, if you use your car for both business and private purposes, you normally work out the allowable business and non-allowable private proportions based on the mileage covered for each.
When filing invoices, remember to note any apportionment on them.
HM Revenue & Customs