What tax could apply to a £300,000 gain realized by a UK insurer on share disposal?

The correct choice for a £300,000 gain realized by a UK insurer on share disposal is Corporation Tax.

When a company, such as an insurer, disposes of assets like shares and realizes a gain, it is subject to Corporation Tax on that profit. This is because Corporation Tax applies to the profits made by companies from activities such as trading, investments, and capital gains. The rate of Corporation Tax varies but is generally applied to the net profits a company earns.

In the context of an insurer, any gain from the disposal of shares falls under corporate activities, making Corporation Tax the relevant tax in this case. This tax is designed to ensure that profits generated by corporations are taxed at a corporate level rather than at the individual level, which is where Income Tax and Capital Gains Tax would apply to individual investors.

Value Added Tax (VAT) does not apply in this situation as it is a tax on the value added to goods and services rather than on capital gains or corporate profits. Income Tax is applicable to individuals and not corporations, while Capital Gains Tax is primarily for individuals on their personal asset disposals. Therefore, the taxation framework for corporate gains clearly identifies Corporation Tax as the proper tax applicable to the gain from share disposal by a UK insurer.