Help figuring out if I need to complete self-assessment for one-off job

Hi! I am confused whether or not I need to fill in self assessment (I do not owe tax) and would appreciate any help. Below are the details: I have been unemployed for several years due to illness (not receiving any benefits). I have never registered for self-assessment before. In the last tax year I had a one off high-skilled (tech) job that paid below the personal allowance but above £1000. We agreed on a deadline for the project (1 week) and my invoice was based on daily rate. That job was the only income I made. I have not received a request from HMRC to file self-assessment. HMRC says I need to complete self-assessment if I'm a sole trader. According to this tool ( https://www.gov.uk/guidance/check-employment-status-for-tax ) I am not because I had no business-associated risks. However, my result says that I count as employed for the purpose of that job, which can't be right since it was a one-off (I presume the tool doesn't account for those circumstances). According to this article ( https://www.litrg.org.uk/tax-guides/self-employment/am-i-employed-self-employed-both-or-neither#one-off-activities ) one-offs may count as neither. And according to this ( https://www.litrg.org.uk/tax-guides/tax-basics/self-assessment-understanding-basics#toc-do-i-have-to-complete-a-self-assessment-tax-return-if-i-have-no-tax-to-pay- ) I may not need to complete self-assessment if I owe no tax, even if I earned above £1000. Could anyone please help clarifying if the above applies to me? Thank you!

Hi ypto,
Your question suggests that you are not an employee of this company, as you are issuing invoices to them, for work that you carried out.
This would imply that you are self employed, as a sole trader.
Where your gross turnover exceeds £1000 in a tax year, you meet the criteria for completing a Self Assessment tax return.
You can register for self employment for Self Assessment here:
Set up as self-employed (a 'sole trader'): step by step.
Your net profit may be subject to Class 2 and Class 4 National Insurance deductions.
The easiest way to check if you need to complete a tax return for 2022 to 2023, is to complete the questionnaire here:
Check if you need to send a Self Assessment tax return
Thank you.