The cuts were laid out by the finance ministry on Monday, after the government made a series of promises in February on tax and social spending.
"We raised our estimate for GDP growth (for 2019) from 3.8 percent to 4 percent, so we expect that this ... will stimulate growth," Finance Minister Teresa Czerwinska told reporters.
The plans disclosed in February -- with an eye on upcoming elections -- included lifting income tax for people under 26, cutting the lowest rate of income tax to 17 percent from 18 percent and increasing tax deductible costs.
The revision forms part of the update of the Convergence Plan that Poland is obliged to send to the European Union by April 30, Czerwinska said.
The cost of lowering the base rate of income tax would be "about five and a half billion zlotys" in 2020, Czerwinska told reporters
The ministry's press officer later tweeted that the cost would be 5.3 billion zloty in 2020. Removing income tax for people under 26 will cost 1.7 billion zloty and changes to tax deductible costs will cost 3.4 billion zloty.
The deficit of public finances is estimated at 1.7 percent in 2019, Czerwinska said.