Unite members will not undertake any overtime, will refuse to work any additional hours or do work not proper to their role in the organisation.
They will also refuse to travel outside of their working time, nor will they work in a location other than their normal place of employment.
This is an important day for Unite members in the Post Office.
They are keen to impress upon their employer their dissatisfaction with the failure to reach a pay agreement with the union and see this an opportunity to protest.
More top news
Girl group 4th Power, a twerking grandmother and a skiving dental receptionist were among the contestants hoping to be the next big thing.
Rain expected in the next 24 hours - no surprise there with it being a Bank Holiday - but there'll also be some brighter skies in places.
ITV releases teaser clips of the final series of the hit historical drama, set to be aired next month.