It has elected for a two-week programme of rolling action by departments, starting on July 25.
The union said the programme has been drawn up "in order to maximise disruption to all Royal Mail services", but also so that no union member is off work for more than two days in the period.
For example, mail centre and cash handling employees will walk out at 7pm on July 25 for 24 hours and at 3am on July 31 for 24 hours, while delivery and collection hub employees will take July 27 and August 2. Other departments will take off various other days.
So far the strike has taken the form of two 24-hour stoppages on Thursday July 12 at 7pm and Thursday July 5 at 3pm. There have been separate strikes by Post Office workers over pay and the closure of Post Offices.
Strike action was called after the union rejected Royal Mail's 2.5% pay rise offer and its plans to modernise, which the union views as leading to unacceptable job losses of up to 40,000 positions.