There are many different ways of valuing a business, depending on the circumstances: for example, based on earnings, cashflow, turnover or asset value. A growing business in a sector with good prospects will be more highly valued than a mature business in a declining industry. Your advisers will be able to provide an indication of what you can expect.
Ultimately, however, your business will be worth what a purchaser is prepared to pay for it. 'Grooming' your business (see 13) can help to increase its likely value.