If you sell certain assets used in a trade this may give rise to a Capital Gains Tax liability. However there is a relief that is available to reduce the amount payable so long as the sale proceeds are reinvested in replacement business assets. Where the whole of the sale proceeds are not fully reinvested then a part of the gain would still remain and hence be taxable.
The reinvestment must be done within a specified time period. This is one year before the date of the sale, or within three years after it.
The type of assets typically involved where Roll Over Relief may be applicable includes land and buildings, fixed plant and machinery and goodwill.
Where sales of assets that may give rise to Capital Gains Tax are concerned you are always best advised to take professional advice on the matter.