Employer Responsibilities

As an employer, you undertake huge responsibilities, not only in regard to the welfare of your employees, but also in complying with government regulation in the deduction of tax and national insurance, pensions and other statutory deductions, and the accounting of these to HMRC on a regular basis.  The penalties for non-compliance or any irregularities can include heavy financial fines and/or imprisonment.

The HMRC has an 'introduction to an employer's responsibilities' here