Question about starting deliveroo second Job

I have a question regarding taxes for a second job I am starting. I am currently working full time and my tax code is S1257L at my main job which I would like to keep the same. I have recently started a side job with Deliveroo making deliveries and my question is will I have to do a self assessment at the end of the year for my second job since I am self employed at my second job? I do not want this to affect the tax code of my main job.

Hi mhofrich Hofrichter,
You will need to register as self-employed and complete a tax return if you earn more than £1000 during the tax year.
It won't change your tax code.
Thank you.