If you are a sole trader or a Limited company who employee and pays more than £116* / week in salary then you must register for PAYE and deduct tax and national insurance at source for your staff.
All such employers have to register for a PAYE Scheme – PAYE i.e Pay As You Earn. This scheme aims at deducting the income tax (PAYE) and National Insurance (NI) from your employee’s salary and pay it to HMRC. The employer is required to contribute into NI (13.8% Class 1) as well. Payroll Tax liabilities need to be paid by the 22nd of the following month