You will only have one obligation which is payment-related.
Once you have registered as self-employed with HMRC you will become responsible for calculating and paying your own tax and National Insurance liabilities. This means that you will need to complete and submit a self-assessment tax return to HMRC every year.
You will then need to pay your taxes and national insurance (NI) in the same way you do when you are employed, however, by being self-employed you can reduce your tax liability by deducting some of your work-related costs such as uniform, travel and phone expenses.
Have a look at this video for more information on how to pay your Self Assessment tax bill.