If the artwork is kept at their home there will be a taxable benefit in kind, which needs to be declared on the annual form P11D.
Say the artwork cost £30,000:
Your client will pay income tax on 20% x £30,000 = £6,000 at their marginal rate, each year. The company must also pay class 1A NICs of 13.8% x £6,000 = £828 per year.
If the artwork is to be kept in a bank vault as a pure investment, there won’t be a benefit in kind charge for you. However, the business must pay the insurance and storage costs, for which there will be no tax deduction. There is also no tax deduction for the cost of buying the artwork as it is not an item used for the business.
If the company closes, any creditors will be able to access the value of that art, just as if it was cash. If the business is solvent when it closes holding significant investments, it may not qualify for entrepreneurs’ relief, which would otherwise reduce the tax you pay on any gain made on the liquidated asset of the company down to 10%.