Mg Mn

Hello, I made an investment of £5000 in a start up company which is eligible for EIS income tax relief. However, my income in the year the shares were issued and the previous year was below the personal tax allowance. Hence, I did not pay any income tax in those years. However, I would still like to claim the income tax relief on my EIS investment as otherwise, I would not be exempt from CGT when the shares are sold. (The rule is, some income tax relief needs to be claimed in order to be eligible for CGT exemption). Is it possible that I can disclaim part of my personal tax allowance in order to claim income tax relief on my EIS investment? I read that according to exclusion 100, it is allowed to disclaim your personal tax allowance but I could not find any more information. If this is the case, should I just send in my EIS certificate along with a letter stating that I want to disclaim part of my allowance? Also, do I need to file a separate self assessment text return because I don't usually file this as my income is salaried from an employer so there's never been a need for a tex return. Many Thanks!