SAYE ShareSave scheme - How much CGT?

[EHammond]

I earn £42k/year and have no other sources of income. I've never had to do a tax return as it's always been handled by my employer (last 20 years).

A few years ago I joined a company ShareSave (SAYE) scheme. Over 3 years, I saved £9k (ended Oct 2013). The share price had climbed significantly, so at the end of the scheme I selected to buy and immediately sell the shares. I received a cheque for £31800 (£22800 profit + my £9k savings). Rather naively, I assumed that tax was handled by the company and that there was no tax liability.

Can anyone explain how I calculate the tax I owe?

[EHammond]

sorry, accidental duplicate. please ignore