One-off Self Assessment payment for prior tax year?

Hi there, I believe I need to declare a payment received from a friend in December 2021 that I now realise is just over the £1,000 limit per tax year and I think is classed as miscellaneous income for a service under BIM100110. All of my income except this one payment has been through PAYE as I have a full time job. I only need to declare that one payment, as such I think I only need to declare self-assessment for that one year and not the current tax year. I understand the first time you register for self-assessment, the government website says you can file for the last four years and that being unaware of your obligation (which I was not until now) is a reasonable excuse to contest a late penalty. I would just like to confirm that this is the case? As I do not have any other tax to declare via self-assessment other than this payment, can I immediately de-register for self-assessment after settling the bill? It's my first time registering for self-assessment and I'm just rather confused, I hope that's okay. When I register, will I automatically be asked to fill a tax return for the current tax year even though I do not need to, or can I just fill in a form for that one year as required? I'm trying my best to do the right thing and want to do my best to avoid making any errors. Any pointers would be amazing. Thank you very much for your help.

Hi

When you register it will ask the date from when it applies and it will automatically look for a return for the last tax year.
Once you have filed the one for 21/22, you can contact us on 0300 200 3310 or webchat to have the 22/23 return withdrawn.
for any penalty that is charged, you can appeal in writing for this to be considered and send it to:

HMRC PAYE & Self Assessment
BX9 1AS

Thank you