Sophie Weids

My adjusted net income for 2023/2024 is £108,951. In order to get my earnings under £100k, do I need to put in £8,951 into my pension or can I put in 20% less as I believe the govt top this up by 20%? Then, I can claim the tax relief on whatever payment I make as its a singular one off payment? I need to make a payment by Friday to ensure I'm under the £100k so I do not lose my childcare. Thanks