Hi Giorgio, welcome to the Crunch Chorus Community Forum! Congrats on your new business venture.
The Self Assessment registration deadline for the 2021/22 tax will be 5th October 2022, assuming you're just starting the sole trade activities now.
This would be for the income from your Sole Trader registration date until 6th April 2022, with it then being due by 31st Jan 2023.
It's a very good idea to keep all your incoming and outgoings nice and organised (Crunch's free software is perfect for this!) to ensure the process is as simple as possible. This article explains how to pay, how much tax you should put aside, and more useful tips.
Hope this helps!