This is normally understood as being synonymous with retrospective pay. It can also refer to the refunding of an earlier mistake or undercalculation of pay. The awarding of back pay by the Labour Court as a result of claims is becoming less common: as John Horgan, former chair of the Court, said on a number of occasions, retrospective pay "is a thing of the past" (a play on words indicating that retrospection refers to the past both in terms of the period in which pay is notionally earned and in terms of the increasiongly unfashionable nature of the concept).
Please note: the European industrial relations glossaries were compiled between 1991 and 2003 and are not updated. For current material see the European industrial relations dictionary.