Assistance Needed Regarding Late Penalty Fine

[edarparis]

Hi everyone!
Not sure I am posting at the right place!
I need some help regarding a late penalty fine.
I received a letter from HMRC last week (February 2025) asking me to pay a fine of £1,600 for not filing my self-assessment in 2009.
In reality, I left the UK in June 2008 following the financial crisis and returned to my home country in Europe. I understand that I should have filed a self-assessment for the one month I worked in 2008, but I completely forgot.
The penalty fee appears to cover outstanding self-assessments from 2009 to 2014. I am concerned that if I pay this fine, HMRC might also ask me to pay a fine for the years from 2014 to today.
Additionally, if they require me to file a self-assessment for 2009, I have no idea what figures to report, as I no longer have records from that time.
Could you please advise on how to proceed?
Thank you.