SEIS loss relief marginal tax rate question

I’m confused as to which marginal tax rate would apply in this scenario below for loss relief against income tax. I sell some SEIS shares for a loss now in tax year 24-25. After April 5th 2025 I fill in my self assessment. I claim for the SEIS loss against my income in the previous tax year 23-24. This is because in 23-24 I earned a significant salary on PAYE resulting in significant tax paid at 45% marginal tax rate. In 24-25 tax year I will not be employed due to a medical condition and thus lower marginal rate of tax likely to be 20%. My question is, if I am claiming the loss relief against the previous tax year where I had paid plenty of tax to cover it and my marginal rate was 45%, what marginal rate will the loss relief against income be based on? Will it be 45% as that was my rate for the 23-24 tax year, or will it be 20% for the 24-25 tax year that i sold the shares in? There are lots of examples online on how to calculate the relief amount based on your marginal tax rate but no examples that explain which marginal tax rate is used when claiming relief against the previous year and in my case these are two very different tax rates. Thank you

Hi,
Please refer to HS286 Negligible value claims and Income Tax losses on disposals of shares you have subscribed for in qualifying trading companies (2024) to ensure you qualify.
Thank you.