Self assessment for extra income <£1000

I am a teacher in the UK. I did some tutoring last year and earned roughly £900. Does that mean I do not need to fill in the self assessment form? Do I need to do anything else?

Hi Chun Nok Maurice Chan,
As your gross turnover from your self employment is below the £1000.00 business income allowance, you do not nee to report this income to HMRC.  
Once you exceed this amount, you will need to register for self assessment as self employed and submit a tax return.
Thank you.