BIM37020 | Wholly and exclusively: statutory background: what the guidance covers: legislative starting point
From HM Revenue & Customs · Business Income Manual
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Starting point for determining tax adjusted profits
The legislation charges tax on the profits of a trade, profession or vocation under for unincorporated businesses and under for companies. Profits are not synonymous with income and are calculated after the deduction of expenses. So you should recognise at the outset that profits are not the same as income.
The starting point for determining the profits from a trade, profession or vocation is the accounts which have been prepared using generally accepted accounting practice (GAAP) (see for unincorporated businesses and for companies). For the definition of GAAP, see in relation to unincorporated businesses and in relation to companies. See also .
The figure of profits from such accounts is then subject to any applicable statutory or case law adjustments for tax purposes. See .
Generally, in order to be deductible for tax purposes, the expenses must be revenue in nature (ie not capital) and be incurred wholly and exclusively for the purposes of the trade. However, there are also a few provisions that provide for specific deductions which would otherwise be denied under these general rules. One example is the costs of incidental loan finance for unincorporated businesses under (for companies such costs are dealt with under the loan relationship rules).