Workers in hundreds of Crown Post Offices are set to stage their 12th round of industrial action since Easter.
Members of the Communication Workers Union in England, Wales, Northern Ireland and most of Scotland will walk out on Monday, followed by a strike in a handful of branches in Scotland on Tuesday.
Staff are also taking other forms of action including a sales ban on financial products and services.
The union is opposed to plans to franchise or close 75 Crown offices, the larger sites usually found on high streets.
More top news
Heavy rain continues across southern Scotland/northern England and the southwest.
Staff at the hospital treating critically-ill baby Charlie Gard have received "shocking" abuse including death threats over the case.
The actor, best known for his role as the dad in Home Alone, was found dead on Friday in his hotel room in Palo Alto, California.