Tax on change from exercise of approved share options

I've noticed a few mistakes in my calculations of my 2018/19 and 2020/21 CGT liability. So I'm trying to recalculate what I should have paid, so I can report the error. But the one part of the calculations that I'm not sure about is how to incorporate the small amounts of cash that I received when I exercised share options. I exercised approved share options in my former company in between the 2017/18 and 2019/20 tax years, and I was told that there would be no income tax or NICs to pay, because their aggregate exercise price was less than £30k. In two cases, my exercise instruction was that the provider should sell enough shares to cover the exercise price, and then give me the remaining shares. When they carried out each sale, the proceeds slightly exceeded the exercise price, so they sent me a cheque for the difference. Let's use the following example, to make my questions concrete: Suppose that I have the option to acquire 110 shares at £1/share, and that the market price is £12/share when I exercise the option. The provider covers the cost of the option by selling 10 shares for a total of £120. They take the £110 exercise cost and give me the remaining 100 shares plus £10 change. My questions are: 1. Is the £10 considered to be a capital gain? 2. If it is a capital gain, should I just add it to the other capital gains that I incurred in the tax year in which I received it, or does it need to be associated with the acquisition or disposal of the 100 shares that I received? 3. If it isn't a capital gain, does it incur some other tax? 4. Is it correct to use £0 as the cost of acquiring the 100 shares in my capital gains calculation?

Hi,

It will depend on the type of share option that was excerised.

Please refer to:

Tax when you sell shares

Thank you.

My options certificates describe each grant of options as a "HMRC Approved Executive Share Option Scheme". Page ERSM300000 of the HMRC internal manual says this is now known as a CSOP Scheme, and it says more information about these schemes is given in ETASSUM40000, but I am struggling to find answers to my questions there. The page that you shared links to HS287, but that doesn't answer my questions either. Now that you know what type of options I exercised, can you please either answer my questions directly or tell me which specific pages in the HMRC internal manual provide the answers?

Hi,
Employment-related securities are securities you acquired because of your employment, when your employer (or someone connected to your employer) gave you (or another person) an opportunity to acquire them.
The most commonly provided securities are: shares in a company (wherever incorporated) or in an unincorporated body constituted under the law of a country or territory outside the United Kingdom (UK) debentures, loan stock, bonds and other debt instruments.  
You only need to complete the ‘Share schemes’ box, box 1 on page Ai 2 if: your employer has not deducted tax from the whole of the taxable amount your employer tells you that the valuation used to arrive at the taxable amount for PAYE, was lower than it should have been — the taxable amount which has not had tax deducted due to this difference should be entered in the ‘Share schemes’ box 1.  
You do not complete the ‘Share schemes’ box for taxable amounts which your employer has fully taxed. Normally these amounts are already included in your P60 (or, where you’ve left employment, P45) which are included in the Employment pages.  Please have a look at helpsheet HS305 for more information by searching www.gov.uk for 'HS305.
Thank you.