The saga started last October, when Alistair Darling, the Chancellor of the Exchequer, announced a new CGT rate of 18 per cent. The subsequent Government climbdown over business asset taper relief and the loss of an effective 10 per cent tax rate is now history and entrepreneurs relief for business owners is now a reality.

Currently, that relief provides a lifetime £1 million of post-April 5, 2008 qualifying gains taxed at 10 per cent.

What's a qualifying gain? At first sight, entrepreneurs' relief has qualifying criteria that are similar to both the old retirement and business asset taper reliefs. However, there are some subtle differences that can catch out the unwary. To start with, if you're a shareholder you must hold at least five per cent of the ordinary share capital of your company, be able to exercise at least five per cent of the voting rights, and be a director or an employee of the company.

Although this is not too onerous, there are many situations in which care is required. Can you also answer these questions positively? Do your business activities qualify? Are you sure you held a qualifying interest for the qualifying period? Are you certain that investment property isn't tainting your qualifying status? Is this an associated disposal which can also qualify?

As with most tax issues, there are a few details to master, according to Carolyn.

She said: "An 'associated disposal' can qualify which, on the face of it, looks quite generous. For example, say you own a property personally which is used by your company's business. In this instance, a sale of the business and property together could give you entrepreneurs relief on both gains. But if you're being paid rent, which makes perfect commercial sense for income tax purposes, that may have just stopped your entrepreneurs relief – at least in part."

Another fundamental difference between the old and new CGT regimes – and one of considerable concern to employees – is the treatment of share options. If you've been incentivising employees with minority shareholdings, will they still pay 10 per cent CGT because they're expecting to benefit from entrepreneurs relief?

"They may have fallen at the first hurdle since entrepreneurs relief sees the reintroduction of a minimum (five per cent) shareholding test," said Carolyn.

"For the last eight years, employees only needed to have qualifying shares – the minimum holding test was abolished in 2000. This could be a major blow for employee share options. With the re-introduction of a minimum shareholding requirement, there may be employees who hold shares or share options who will be paying 80 per cent more CGT than they might have expected."