K4153 Tax Code - what does it mean and what can I do about it?

Hi, I have been given this Tax Code K4153 and do not understand what its for. I have been in the PAYE system for many years and never seen anything like it before. I tipped over into the 40% tax bracket last year (2023-24) and have 2 private pension pots one of which I have just drawn down. I have phoned Inland Revenue twice waiting an hour each time. The first agent was not been able to explain so I understood and then said "that doesn't look right" but nothing happened. The second agent after I had explained my situation said "just a minute and put me on hold while the hold music played, the call went quiet and about a minute later the call dropped! Aaagh! I am very concerned about this situation and what will happen to my take home pay in April. I have thought about seeking private advice to find someone to help and explain but thought I would post here first to see if anyone could offer some advice on what to do. The thought of going back into the IR phone system again is not appealing. Why can't we online message or EMail them? Anyway, all thoughts and advice welcome! Many thanks

Hi Tony Britton,
If you have an online peronal tax account you can view the breakdown of the code here:
Personal tax account: sign in or set up
We would need to access your record to review the code so you will need to contact HMRC if you are unable to view the code online:
Income Tax: general enquiries
Thank you.