This Practice Note examines the nature of zero hours contracts. It includes absence of mutuality of obligation, casual workers, as required or as needed, employment contract without obligation, piece work, on call, flexibility, over-arching or umbrella contracts, assignments, employee or worker status, continuity of employment, national minimum wage (NMW), statutory sick pay (SSP), working time and holiday entitlement and accrual, discrimination protection, part-time workers, pension auto-enrolment, TUPE 2006 and the pros and cons of zero hours contracts. It does not cover the statutory protections available to workers and employees on zero hours contracts and on lower incomes, relating to unenforceable exclusivity clauses and protection from detriment and unfair dismissal. These are covered separately in Practice Note: Exclusivity clauses—protections for low-income and zero hours workers. In this Practice Note, we use the term ‘employer’ to mean the hiring party in a contract for work, whether or not the individual being hired is an employee or a worker. We generally use the term 'worker' (which includes an 'employee' in the narrow sense) for the individual undertaking the work, unless the