Claiming tax relief on a AVC lump sum.

I have a NHS Prudential AVC. I am in the fortunate position of having a large lump sum of cash that I would like to invest in it. For lump sum payments tax relief must be claimed from HMRC by me, rather than at source. I am confused about how much I can invest using Carry Forward and do not understand what calculations I must make when writing to HMRC to claim the tax relief. As an example - I earn £40k gross and wish to invest £60k. I think I can invest up to my gross salary for each year, but do I not have to take into account employer pension and NI contributions? Is this a simple subtraction based on my P60 of gross salary, minus NI contribution, minus employer pension contribution? Thankyou.

Hi JimMcN,
Please refer to guidance here:
Tax on your private pension contributions.
Thank you.