Paying into SIPP

Hi, I'm completing my Self Assessment as I have paid into a SIPP. I have paid the correct tax for 2023-2024 based off my income but when I provide the SIPP amount (£6375 after adding the relief at source - my contribution was £5000) then my Self Assessment calculation says that I owe another £360 tax! It seems the £6375 is added to the basic rate bracket at 20% and my salary at the higher rate (40%) goes down by that amount. I was under the impression my amount of taxable income would go down by the SIPP amount so I should save moey rather than pay more tax! Have I misunderstood or have I done something wrong?

Hi,

Unfortunately, it is not possible to review personal matters in this forum. For individualised assistance please contact our Self Assessment team for advice:
 
Self Assessment: general enquiries
 
Thank you.