Hi Alan Clifford!
Welcome to QuickBooks Community. Let me assist you in adding P45.
You can update your tax profile and add it from there. Go to the Gear icon and select Tax Profile. You have a set allowance and in the personal allowance section you would need to adjust that amount to how much allowance you have left or if that personal allowance amount is less than your PAYE you would need to adjust it to zero. This will mean your Tax is then calculated based on the allowance you have used.
Check this article to ensure correct calculation of your self-employment taxes: QuickBooks Self-Employed UK Tax Profile Set Up.
Also, you can refer to this article in filing your taxes: Year-end Taxes.
I'm right here if you need additional help. Just let us know by commenting below. Take care always.
