Your employer gives you shares as part of a Share Incentive Plan (SIP).
Income Tax and National Insurance
No income tax and national insurance payable if you hold the shares in the scheme for 5 years. If take the shares out of the scheme to sell or dispose of them sooner, income tax and national insurance will be able.
4 ways you can get shares under SIPs.
Capital Gains Tax
You are not liable to Capital Gains Tax on shares if you keep them in the plan until you sell them. If/when you take them out of the plan and sell them you are liable to Capital Gains Tax if the value has increased subject your normal annual capital gains allowance remaining, if any.