"115,000 postal workers will strike for a proper pay rise," the CWU said on Twitter on Tuesday.
The strike will take place on four days: August 26 and 31, and September 8 and 9, according to the statement. All protests will begin at 4 a.m. local time (03:00 GMT), the union added.
The workers have decided to organize the strike due to low wages amid record inflation, given that Royal Mail has made a profit of 750 million pounds ($908 million), while also paying 400 million of pounds in dividends to shareholders of a company whose leaders already receive "millions," the CWU said.
The majority of postal workers, 97.6%, have voted to go on strike even despite Royal Mail offering a 5.5% pay increase, according to the union.