There are very few HR policies that are a legal requirement. Here is a list of policies that are (or we strongly advise that all businesses should have):
Beyond that list, consider any other policy that helps in the communication of rules and procedures to staff, that helps meet the needs of your business, or is designed to protect the interests of your business.
Any policy / handbook should always be clear, user-friendly and easy to understand. Our team can provide templates or bespoke policies informed by our legal and HR experience.
When any employer is creating a new policy, or staff handbook, or reviewing the same, you need to be mindful which (if any) terms are contractual. You will generally want to make policies and procedures non-contractual because to remain as agile as possible as a business you need to be able to change them without seeking the agreement of the staff to which they apply (which would be the case if they were contractual). Those staff will remain bound by amended non-contractual policies because of their implied duty to obey lawful and reasonable orders.