Thousands of workers at HM Revenue and Customs are to be balloted for strikes in a long-running campaign over jobs and cuts.
The Public and Commercial Services (PCS) union said 50,000 of its members will vote in the coming weeks on whether to launch a campaign of industrial action.
The ballot is part of the union's national campaign among its 250,000 civil service members against cuts to jobs and services.
The union said it has asked HM Revenue and Customs (HMRC) to reach a joint agreement on staffing levels and to make a joint case to the Government for long-term investment to tackle tax avoidance and evasion.
PCS has been campaigning against the closure of HMRC's 281 walk-in inquiry centres, warning it will cut face-to-face tax advice for millions of people and put 1,300 jobs at risk.
The ballot closes on May 16, with plans for a series of one-day strikes in the event of a yes vote.
PCS general secretary Mark Serwotka said: "A decade of cuts has left HMRC unable to cope with its crucial job of collecting the taxes that fund the other public services we all rely on.
"These cuts must be stopped and the Government must invest in our society and a serious clampdown on the tax dodgers who deprive our public finances of tens of billions of pounds a year."
An HMRC spokesman said: "We remain committed to resolving disputes through dialogue, making industrial action entirely unnecessary."