Chattels: exempt and chargeable gains: marginal relief
If the consideration for the disposal of a chattel is greater than £6,000, the chargeable gain may be restricted.
When a chattel is disposed of for more than £6,000 see CG76573, you calculate the difference between the disposal consideration and £6,000 then multiply that difference by 5/3. The answer is the maximum chargeable gain.
If the actual chargeable gain exceeds that amount, you exclude the excess and assess the smaller amount. If the actual chargeable gain is less than that amount, you assess the actual gain.
If the disposal consideration is £15,000 or more, the maximum chargeable gain exceeds the actual chargeable gain and no marginal relief is available.
CG76612 shows you an example of marginal relief.