If you were working from home on a regular basis during the tax year ending 5 April 2021, you will be able to claim £6 per week without any need to keep evidence of extra work.
If you incurred additional costs above this weekly limit, you would need to keep receipts and bills in order to claim the allowance.
The total tax relief will depend on your tax rate. For example, if you pay tax at 20%, your tax saving will be £6 per week at 20%, which will be £1.20, saving you £62.40 against your tax for the full year.
Related Article: HMRC advisory fuel rates