There are a number of things you can do to get help with your self-assessment tax issues, such as:
HMRC will be able to offer you advice on registering and paying tax via self-assessment. They will definitely be able to help with simple issues but for more complex things you may need to contact someone else.
Ask an Accountant
When I first switched to paying self-assessment tax, I was completely confused about the whole process. I contacted a firm which offered accountancy in Essex called Applemed LTD. They were able to offer me all kinds of advice and guide me through the process.
Ask a Friend
If you don’t have the budget to pay for an accountant then you could try asking around your friends and family to see if anyone has experience in registering for self-assessment tax and you may be able to get some free advice.