Old Self Assessment Tax Bill

Hi I have an old Self Assessment Tax Bil for the period ending 2020 (Covid) since then I’ve had a couple of job changes and P45/P60 have been issued but my personal tax code has not changed to reflect the bill yet now I’ve been chased up for payment? The previous companies accountant couldn’t see any overdue tax when calculating my pay etc

Hi
If you are unsure of why the bill has been generated you will need to contact our helpline so we can view the calculation.
Income Tax: general enquiries
Thankyou.