Over 50,000 Revenue and Customs workers are to walk out tomorrow in protest at "massive cuts" which they say have undermined efforts to clamp down on tax avoidance schemes.
Members of the Public and Commercial Services union (PCS) will take strike action across Britain.
It said that offices will be closed and telephone calls unanswered as a result.
The union said 30,000 jobs have been axed since 2005 and a further 10,000 are set to go in the near future, "undermining" efforts to investigate schemes such as the one used by comedian Jimmy Carr which sparked a political row last week.
The PCS said an estimated £120 billion was lost every year because of tax evasion and avoidance, and the HMRC did not have enough resources to tackle the problem.
The strike is also being called in opposition to "creeping privatisation" in the department, which is trialling the use of private firms to handle tax credit inquiries.
PCS general secretary Mark Serwotka said: "It is sickening to see millionaires in the Cabinet wringing their hands about the immorality of tax avoidance when it is their lack of political will to act that means we lose tens of billions of pounds every year.
"The case for investment in our public services as an alternative to austerity could not be more obvious than it is in HMRC.
"Yet the government wants to cut 10,000 more jobs from the department, letting the wealthy tax dodgers off the hook and punishing the rest of us for a recession we did not cause."
An HM Revenue & Customs spokesman said: "We are seeking dialogue with the PCS to address their concerns and will work to minimise any disruption to our customers."