What are the minimum policies an HR function in a CSO should have?

We’re a team of six and we’ve been going about four years. We have a basic staff handbook from when we started but it’s very thin — leave entitlements, a bit about conduct, that’s about it. We’re about to take on new staff for the first time in a while and it’s made me realise how much we’re probably missing. What are the actual must-have HR policies for an organisation our size? I’m not looking for a massive HR manual but I want to make sure we’re covered on the things that matter legally and practically.