What do I need to sort out when I take on my first employee?

As a minimum you'll need to: register as an employer with HMRC, choose and set up payroll software, collect the employee's details (including their P45 or a starter checklist if they don't have one), agree and record their salary and hours in a written contract, assess them for pension auto-enrolment, and start sending FPS submissions to HMRC from their first payday. You'll also need employer's liability insurance in most cases. Because getting any of these wrong can create compliance issues later, many first-time employers hand payroll setup to a bookkeeper for peace of mind.