SA Late filing penalty

Hi there, I am a salaried employee. I am working from April 2022 in UK. Tax component gets detected from my salary on monthly basis. I haven't submitted any self assessment tax return in the past. As per the HMRC guideline, I no need to submit the self assessment tax return. but I got a letter from HMRC few days back, for SA late filing penalty notice for year 2022 - 2023. I really don't understand why I got this letter now. I don't have any tax due, but still they are asking me to pay the late filing penalty. I tried to reach out to different team in HMRC over call, they finally asked me to submit the self assessment tax return, then go for a appeal. How long it will take to get out for this penalty if I go for a appeal.

Hi,
Please see information here:
https://www.gov.uk/guidance/check-when-to-appeal-a-self-assessment-penalty-for-late-filing-or-late-payment
Appeal a Self Assessment penalty for late filing or late payment
Thank you

I don’t see enough information on this page. It simply says that apply online or post.