2 jobs in same tax year and also a soletrader- How to fill in Self Assessment

Hello, I worked for a company from Nov 21 to Aug 22 and resigned and joined another company from Aug 22 and still working there. and for both jobs i paid tax through my employer. Whilst i was at the first company, i setup a soletrader account on Amazon only for about 3 months (from Mar 22 to May 22) and have since closed the account. I did not make more than £1000 in profits as a sole trader but I received a self assessment form in June last year which i think is because of the sole trader account i setup. I informed HMRC via the online form that i was never self employed (as i was in fulltime employment during the tax year) and also didnt make up to threshold to complete a self assessment for the sole trader job. But i recently received the penalty letter because i hadnt completed the self assessment form. Can i please understand why that is the case? As i am confused as to why i would have received a penalty if i already told HMRC that i was not self employed. My second question is- if i still have to complete the form, do i need to fill in a return for the 3 jobs i had in 22/23 tax year (even though the sole trader didnt make up to £1000K profits)? or just the 2 jobs. Thanks

Hi Ifeoma,
If you had two employment, you would complete SA102 for each employment and if online, select 2 for the number of employments.
For your self employment you would complete either SA103S (short) or SA103F (full) to declare your self employment.
For an online tax return, you would tick yes to self employment and select 1 for the number of self employments in the tax year.
Thank you.