Personal allowance

I have just completed my self assessment. The question I have is why has my personal allowance changed on the tax calculation which does not reflect the tax code which was constant for the entire year. My tax code did change on 6th April 2023 and again on 11 July 2023. But neither code correlates with the amount in the calculation. The self assessment doesn’t ask for your tax code so how have HMRC calculated this. I appreciate tax codes change but should HMRC not have used the code I was given for the entire year and then change it for subsequent years, which they did.

Hi
Your tax code is based on an estimated income during the year along with any potential company benefits received. when your tax return is submitted, this shows the actual income and any benefits received and these figures may be higher which means a different rate of personal allowance is applied.

Thank you for clarifying.