Newly self-employed on top of PAYE

Hello, Please could someone offer some clarification on the following: I have just started a new part time self-employed role. This is in addition to an existing role with an employer where my salary is paid monthly using PAYE. I understand that my first self assessment will not need to be until the next tax year (25/26) for self employed earnings this current tax year (24/25). I understand that I don’t need to register as self employed/sole trader until I submit my first self assessment tax return as I haven’t had any additional income in the last tax year (23/24) to warrant a self assessment. Please can you verify this is correct? When I do submit a self assessment which would include information from my P60 for my PAYE job. (Estimated annual salary £20k so tax will be paid on the amount from £12571 upwards)) do I then receive a bill for the declared self employment income which I pay separately? Or does HMRC notify my employer to pay the additional self employment income via PAYE? Do I get to choose how to pay my additional tax bill? Can I prepay upfront in anticipation of my tax bill?

Bumping up - can anyone help?

Hi,

If you need to complete a tax return and have not sent one before, the deadline to notify us is 5th October. So if you started your self employment in 2024 to 2025 you must notify us of your need to complete a Self Assessement tax return by 5 October 2025. You can do this by registering for Self Assessment. You can find more detailed information on Self Assessment here: 

Self Assessment: detailed information

Please note, if you complete a paper return, this must be done by 31 October 2025 but if you choose to complete the return online the deadline will be 31 January 2026. 

You will also need to pay the tax you owe by 31 January 2026.

You can view the different ways in which you can pay the additional tax you owe here:

Pay your Self Assessment tax bill

Thank you.