P60 vs Self Assessment Calculation

I changed job in June, and had my tax code changed as I had a letter saying I owed tax as I had underpaid in this job. My code went from C0T to CK115X as there was an estimated underpayment of £419. When I’ve come to do my self assessment form, the tax paid by me on the calculation differs by £5k from that on my P60 for the same year. This is obviously before I changed jobs and so I wanted to know:- When I submit my calculation (completed self assessment return) is the £5k owed adjusted for the increased tax payments since June? Should I have added this in my self assessment form? NB the only income on the self assessment is my salary as all benefits were covered by my former (and current) employer including the tax element.

Hi,
Your 2023 to 2024 return should only include income earned and tax paid between 6 April 2023 and 5 April 2024.
As such, you should not include any pay or tax from the 6 April 2024.
If you would like to discuss your calculation in more detail, contact our Self Assessment team by webchat or phone via:
Self Assessment: general enquiries
Thank you.