Tax offices throughout the country would close on Feb. 4, 5, 10 and 17, the POE-DOY union President Yannis Grivas said.
A mix of planned wage freezes, cuts in allowances and tax changes would reduce tax officials' earnings by about 25 percent, the union said. Allowances form a large part of Greek civil servants' income.
"We are willing to accept an 8 percent wage cut, but not 25 percent," Grivas told Reuters. The union will decide next week whether to call more walkouts.
Customs staff also announced they would go on strike on Feb. 11 and 12 and the civil servants' union federation ADEDY has already called an one-day stoppage for Feb 10.
Protests and demonstrations are a threat to Greece's three-year plan to reduce its budget shortfall and avoid becoming the euro zone's first country to face penalties for running an excessive deficit.
Greece has been hit hard on international markets, with bond yields soaring and shares plummeting, after it said in October its 2009 deficit had swollen to 12.7 percent of gross domestic product.
Greece's European Union partner, worried they may need to come to the indebted country's rescue are pressing for Irish-style pay and pension cuts to reduce deficits and the euro zone's biggest debt-to-GDP ratio.
"Our pay cuts will be twice as big as in Ireland," Grivas said. Greek tax officials earn an average 2,400 euros a month.
Among the measures announced by the Socialist government is a public sector wage freeze for those earning above 2,000 euros ($2,812) a month.
"The EU must realise that Greece's biggest problem is tax evasion, as president of the tax collectors' union I'm the best-placed person to know this," Grivas said.