Workers covered by the Working Time Regulations must not be required to work more than 13 hours per day. Also individuals must not be required, against their wishes, to work an average of more than 48 hours a week. Workers may agree in writing to work more than the 48 hours per week on average, and can withdraw their agreement at any time.
The hours that an individual works in a week are averaged out over what is termed a 'reference period'. A reference period of 17 weeks is normal.
There are exceptions to the formula for calculating the reference period for certain industries and occupations, and where the employer agrees a collective agreement or workforce agreement with employee representatives.
There are different rules for mobile transport workers and tighter rules for young workers aged 16 and 17.