The deadline for registering for Self Assessment is 5 October following the end of the tax year,
You must tell HMRC that you need to prepare a tax return if you have any of the following:
- Self employed income (sole trader, freelancer, partner etc)
- Made a capital gain.
- Have employment income not taxed under PAYE.
- Have received any dividend income and further tax to pay on that income.
- Any other untaxed income or are liable to tax at higher rates.
- Are due to repay any child benefit
You can register with HMRC for self-assessment here.