Communication Workers Union members will vote in late September on the dispute with the result due on 8 October.
Royal Mail said it was disappointed that a ballot had been called while discussions with the union were still ongoing, though the union believes an agreement last year on pay and reform pensions is not being honoured.
The postal group last year agreed to a reduced 35-hour working week, a pay rise and pension changes.
Unions are accusing new chief executive Rico Black of backtracking, something the company denies and says it has put through two pay rises over the past year and reduced the working week by an hour.
Black took over as CEO from Moya Greene last year but has seen the share price slide well below its 2013 float price of 330p under his tenure.
His appointment last year was also immediately embroiled in controversy after it emerged he paid no tax on a £5.8mln ‘Golden Hello’ when he took the job.
Royal Mail’s last national strike was ten years ago.
Shares were flat at 199.2p.