What was the case about?
Mrs Brazel was a visiting music teacher at a school run by the Harpur Trust (the Trust). She was a worker employed under a permanent contract on a zero hours basis. During term time, Mrs Brazel worked different hours each week (depending on how many pupils needed music lessons).
Mrs Brazel was entitled to 5.6 weeks' paid holiday each leave year under her contract. She was required to take her holiday during the school holidays, when she was not giving music lessons.
Before September 2011, it was agreed between the parties that Mrs Brazel would take holiday in three equal tranches in the year. Her holiday pay was calculated by taking her average weekly pay in the 12 weeks prior to the school holiday (ignoring any weeks she did not receive pay) in accordance with relevant employment laws. This was described by the Supreme Court as the "Calendar Week Method".
From September 2011, Mrs Brazel's holiday pay was calculated as 12.07% of her earnings in the preceding term (described by the Supreme Court as the "Percentage Method"). The 12.07% calculation was used to acknowledge that out of the year (52 weeks), 5.6 weeks would not be worked due to holiday = 46.4 weeks. 5.6 weeks is 12.07% of 46.4 weeks.
Mrs Brazel claimed she was being underpaid holiday by using the 12.07% Percentage Method. An employment tribunal rejected her claims, but the Employment Appeal Tribunal allowed her appeal. The Trust appealed to the Court of Appeal who dismissed their appeal. The Trust subsequently appealed to the Supreme Court.