A contract, or written statement of employment, is required by law to be given to all paid employees who have been employed for at least a month. Having a contract in place helps to avoid any misunderstanding should things go wrong between an employer and an employee.
A contract of employment should set out in clear terms the details of:
rates of pay
hours of work
sick pay entitlement
disciplinary and grievance procedures
The contract should be signed by the employee and reviewed on a regular basis (usually as part of an annual appraisal scheme). If your organisation uses agency workers, check the regulations and guidance on the ACAS website.