Tax relief on back pay

Good morning, I'm about to receive 2 & half years back pay which will put me over the 100k for this tax year (24-25) and I'll will start to loose my personal allowance. The previous years l did not earn 100k. Is there a way of off setting this/using previous years allowance? If so what do l need to do? Thanks

Hi,
Unfortunately this is not possible, your liability for tax is in the financial year you receive the income, not when the income is generated. 
Thank you.