All the hours necessary……
Even if an employee has voluntarily opted out of the 48-hour working week, they are still legally entitled to take the daily and weekly rest breaks that are provided for in the Working Time Regulations 1998 .
You can’t make them work “all the hours necessary” to get the job done.
As rest breaks should add up to 90 hours per week an employee’s total working hours should add up to not more than 78 hours per week on average.
It’s an average because some rest breaks can be taken either in the week that they fall due or as a period of rest.
You need to calculate the average weekly working time over 17 weeks.
Where an employee has voluntarily opted out of the 48-hour working week, they are still entitled to daily and weekly rest breaks under the Working Time Regulations 1998.
As these breaks add up to 90 hours, they should not work more than 78 hours per week on average.