Hi,
In the current tax year, you can claim tax relief on pension payments up to the amount of income from employmnent or self employment or £60000, whichever is the lower.
Your pension provider claims tax from HMRC and you enter the gross payment, your payment plus tax claimed, in the tax return, so that any additional tax relief due is claimed. Although you can pay more than the tax free threshold into your pension scheme, any amount above the threshold, does not qualify for any relief, so is taxed as income.
You can carry forward any unused earnings threshold from the 3 previous tax years and add it to the current year threshold, so that a larger payment can be made and still qualify for tax relief. Any payments over the threshold should be declared on SA101 supplementary page of a Self Assessment tax return. You can see guidance here:
Check if you have unused annual allowances on your pension savings
Thank you.