Wrong leaving date on P45 generated by previous employer

My previous employer has generated P45 with wrong last working day. They accepted their mistake and provided me the 'Statement of Earning' with correct leaving date and the same I have submitted to my current employer and the current employer has notified HMRC about it in Nov 2023. But again this month (Dec 2023) HMRC has changed my Tax code considering my wrong working day on P45. What should be done so that the correct date will be reflected to HMRC side and my tax code will be corrected. I have tried to contact my previous employer asking them to do the needful and contact HMRC but they are not replying. This all issue is causing me unnecessary tax cut . Could you please suggest the way forward?

Hi
If the incorrect date was submitted by the employer then they should submit the amended details online.
If your previous employer will not do this you can submit the letter they gave you with the correct details to HMRC at
HMRC,
Self Assessment & PAYE,
BX9 1AS
UK.
If you tax code is incorrect then you will need to contact HMRC to review.
You can contact HMRC atIncome Tax: general enquiries