You're generally allowed to contribute as much as 100% of your earnings or up to £60,000 every year (known as the annual allowance), whichever is the larger amount.

If you have previously not used your full annual allowance, you can normally carry foward any unused allowances from the last 3 tax years. 

For very high earners, the amount you can put into your pension might be less than the standard annual allowance. This is because you might be subject to the tapered annual allowance, which applies to people earning over £240,000 annually.