Best way to file taxes as a 30 hour per month 2nd job

I have 2 jobs. My main job is full time and I get paid though an employer who takes my NI contributions and taxes at source. My 2nd job is part time and I work from home with flexible hours. I carry out paid administrative work for charity and submit invoices each month for hours worked (variable). Should I set myself up as limited company? What is the best way for me to ensure I am paying the correct taxes for the 2nd job please?

Hi,
To pay the tax due on your second job, you may prefer to set up as a sole trader, you would declare your earnings and employment income at the end of the year by submitting a tax return, and pay any tax and National Insurance that your return calculates as being due. You can see guidance here:
What a sole trader is
Or you can contact our Self Assessment team for advice:
Self Assessment: general enquiries
Thank you.