Tax code change due to backdated pension

Hi, I started at a new company in April of 2023. My tax code during April - June was 1257L, however, my pension contribution was not in place until July 2023, when I had backdated pension contributions taken from my salary. Since then (July 2023) to now my tax code is 1009T M1. Will my tax code be reviewed in April 2024 or is this something I should contact HMRC to discuss? Additionally, does the 1009 in my tax code mean my tax free allowance is lower than if I was on tax code 1257L and am I due a tax refund for this? Thanks

Hi,

The 1009T M1 does mean the your tax free allowance is lower. You will need to contact our Income Tax team to review the tax code.

Income Tax: general enquiries

Thank you.