Treat it as a formal process from the moment it lands, even if your gut says to explain why they've got it wrong. Acknowledge it in writing, follow a clear procedure, investigate where you need to, hold a meeting to hear them out, give a reasoned outcome, and offer a right of appeal.
Done properly, the process protects you even if the complaint doesn't really stack up. Brush it aside and a weak complaint can still turn into a costly claim, because a tribunal looks at how you responded, not just at what was raised.
Every situation has its own details, and those details change the right answer. For a read on yours, take the free Employee Situation Check or book a call.
Watch
How to handle this, in a couple of minutes
Samantha talks through the practical steps.
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.