Can I let someone go during their probation?

Usually yes, and more easily than later on, but probation isn't a blank cheque. You still need a fair reason and a fair, if shorter, process, and some claims like discrimination apply from day one whatever the length of service.

The trick is to actually use probation: set expectations from day one, give honest feedback early, and don't leave the hard conversation until the final week.

One thing to know before January. From 1 January 2027 staff can claim unfair dismissal after six months instead of two years, and the compensation cap is scrapped. There is no statutory probation period to fall back on, despite what a lot of HR commentary still says, so your own probation clause is the only protection you have. If yours runs six months, you have no margin at all, because the moment it ends they already qualify.

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.