You can enter the transaction amount as your other income in your tax profile. Transactions entered while setting it up will not be included in the calculation of your estimated taxes.
To start with, if the said income is one of the transactions downloaded from your bank, you'll have to exclude it from the list. Let me show you how.
Once done, let me show you how you can enter it directly in your tax profile:
In addition, here's an article you can read to learn more about how you can prepare your tax profile: QuickBooks Self-Employed UK Tax Profile Set Up.
Lastly, I've also included this helpful article to understand more about how our account works while working with your business with us: QuickBooks Self-Employed Overview.
If you have any other questions, please let me know in the comments below. I'll be here to help. Stay safe always!