There are limits to the total amount that can be contributed into pensions in each tax year.
If you're a UK taxpayer, the standard rule for the 2019/20 tax year is that you'll get tax relief on pension contributions of up to 100% of your earnings or a £40,000 annual allowance, whichever is lower.
Any contributions you make over this limit won't attract tax relief and will be added to your other income and be subject to Income Tax at the rate(s) that applies to you.
There are additional rules which apply if you are a non-taxpayer or have triggered certain conditions. Please visit the money advice service website for more information regarding tax relief on pension contributions.