If you employ anyone, register with HMRC as an employer before the first payday to get your employer PAYE reference. You cannot register more than 2 months before you start paying people.
You must register for VAT if your taxable turnover for the last 12 months goes over £90,000, or you expect it to go over £90,000 in the next 30 days alone. You can register voluntarily below the threshold.
Register as an employer (PAYE)
What you need before you pay your first employee.
Check if you need to register for VAT
How the threshold works and when registration is due.