What is the maximum pension contribution I can pay?

In each tax year you can pay personal pension contributions of up to the lower of (1) 100% of your earnings and (2) the annual allowance of £50,000 (was higher before 2011/2012 and due to drop to £40,000 after 2013/2014).

Earnings means your taxable income from jobs and self employment.

You cannot carry back pension contributions and you cannot carry forward any shortfall in your payments and pay them in a later year. Any unused annual allowance can be carried forward for up to 3 years. The annual allowance is for you pension input period which is usually (but not always) the same as the tax year.