Paying income tax after retirement on a pittance paid for reviewing things

If you're retired and pay tax on your workplace pension but fancy reviewing things and completing surveys for something to do, do you have to pay income tax on any pay. Eg, You can earn £10 from time to time by completing surveys. If you have to pay income tax, how do you do it?

Hi,
You can earn up to £1000 tax free each year.
If more than this you will need to register for self assessment and report it as self employment.
Thank you.