Voters have until Friday 16 March to have their say - either by post, online or by phone - and the results will be considered at a special meeting of the union's elected national executive on 19 March.
The union is currently talking to other unions with members across three public sector pension schemes - civil service, education and health - with a view to taking co-ordinated industrial action on 28 March and beyond, as well as other joint campaigning activity.
The union's NEC has unanimously rejected the government's latest offer, as it would force public servants to work up to eight years longer for a worse pension in retirement, and to pay more in contributions with the money going straight to the Treasury to pay off a budget deficit caused by the failures of bankers and successive governments.
The government's proposals are designed to make it easier to privatise more of our public services, the union says - a point acknowledged by Treasury minister Danny Alexander when he told the Commons in December the plans would make pensions "substantially more affordable to alternative providers".
PCS general secretary Mark Serwotka said: "We're asking people to send a clear message that they refuse to be bullied into paying more and working longer for less, simply to pay off debts caused by the failures of bankers and politicians.
"While we will continue to meet government ministers, until they start negotiating on these key issues we will continue to plan for widespread, co-ordinated industrial action across the public sector."