The business is carried on by a company and the proprietor is an employee and shareholder of the company.The company's profits are chargeable to corporation tax, but in computing those profits, your remuneration may be deducted.
Your remuneration is relevant earnings for pensions planning purposes. You may take out a personal pension scheme or the company, or may set up an occupational pension scheme.
With the introduction of the national minimum wage, for which the HM Revenue & Customs is the enforcement agency, the HMRC may argue that a dividend should be characterised as remuneration. That would result in the need to operate PAYE.
The company may also provide a car. You can claim capital allowances for the cost of the car and the running costs, but you will be liable to income tax under the fringe benefits legislation.
Where any form of loan or advance is made by the company to the shareholder or a member of the shareholders family, then the company has to account for tax at 25% of the amount advanced and not repaid within 9 months of the end of the accounting period. That tax is repaid if the advance is written off. If the advance is written off then the individual is taxed on the sum written off as a dividend.
If the business sustains a loss, that loss is trapped inside the company. It may be set off against profits of the preceding accounting period. But the situation may arise where you have to pay income tax on remuneration, while the company has losses which can only be carried forward.