Missed capital gains tax

Hi, I am self employed. I sold a property in May-2020 but did not report to HMRC (Did not submit CGT). I also submitted tax return for TY 2020-21 but did not include the gains. It was residential property. Do I need to Amend the Tax return TY 2020-21 and include the CGT summary? And/Or Do I need to submit paper based CGT? Do I need to do both? I also sold another property in October 2022 (Residential property) but I did not submit report to HMRC (Did not submit CGT) But, I have included the gains in my tax return TY 2022-23 and paid the taxes on gains. Do I need to submit CGT separately? I tried to submit CGT online, but at some point they asked me ' Did you submit self assessment tax return for TY 2022-23' I have selected 'Yes' Then they said 'You can not use this service' what does it mean?

Hi

For 20/21 you will need to do both. For 22/23 you need to submit the paper property disposal return -  Report and pay your Capital Gains Tax.
You cannot use the online service as you have since submitted the tax return.

Thank you