Do I have to put someone on a performance plan before dismissing them?

No law says you have to use something called a performance improvement plan. But you are expected to show that, before dismissing for poor performance, you gave honest feedback, a fair chance to improve, and real support to get there. A plan is just the tidiest way to prove you did all three.

Skip that stage and you've got the usual reason a performance dismissal is found unfair, even when the work really was poor. A short, specific plan, with clear standards, a sensible timescale and regular check-ins, protects you, and often fixes the problem without a dismissal at all. The versions that backfire are vague targets, or a 'plan' that's really just a countdown to the door.

General guidance to help you decide your next step, not legal advice. Employment law changes, so always check the current position for your own situation.