You should not be aiming to avoid it. What you can do is make sure you claim every relief you are legitimately entitled to, and that the sale is structured and timed properly before you commit. That is a job for a qualified accountant or tax adviser, ideally engaged well before you agree a deal.
Capital gains tax is charged on the gain when you dispose of an asset — in a business sale, typically shares in the company or the trade and assets themselves. Whether you pay, and how much, depends on what is being sold, how long you have held it, your role in the business, how the proceeds are paid, and your wider income position in the same tax year.
There are established statutory reliefs that reduce or defer a charge in the right circumstances. Business Asset Disposal Relief can apply a lower rate to qualifying disposals by people who meet conditions on shareholding, employment and holding period. Rollover, holdover and incorporation reliefs can defer a gain where proceeds are reinvested or assets are transferred. Gifts and transfers to a spouse or civil partner have their own treatment. Each has strict qualifying conditions, and the rates, the annual exempt amount and the lifetime limit on Business Asset Disposal Relief are set by government and change — check the position for the tax year of the disposal on gov.uk.
The practical point is that eligibility is usually decided by things you did months or years earlier — how shares were issued, whether the company holds non-trading assets, whether you draw a salary. Once the sale is signed, most of those levers have gone. Talk to your accountant early, and be wary of any scheme marketed to you as a way to remove the charge entirely.
We arrange asset and business finance. We do not advise on the tax treatment of a sale and we cannot tell you whether a relief applies to you.
This is general information, not tax advice. Confirm your own position with your accountant or HMRC.