A new study shows the Irish tax system will hit record highs this week, as it comes into effect from 1 February.
A key issue will be the threshold for the first €2,000 of taxable income and the threshold of income tax payable.
The new tax system is the first of its kind in the eurozone and will impact businesses across the island.
In a statement, the Department of Finance said it was a key step towards protecting businesses from tax increases.
The study by the Irish Institute of Economic Research (IIE) showed the Irish system would hit record levels of taxable incomes and tax on earnings of €4.6 billion in 2019.
The rate of tax would rise from 20% to 25%, with the highest rates in Dublin at 35%.
The report also showed that €6.4 billion of taxable earnings would be taxed in 2019 and the average tax rate would be 39%.
There are two ways to increase taxable income.
The first is by increasing the threshold to €2.3 million.
This will raise the amount of income subject to income tax from €5,000 to €10,000.
The second is by reducing the threshold.
This means a person with taxable income of €5 million will pay a lower rate of income taxes.
This will be implemented in 2019, with the second step being phased in over three years, from 2019 to 2020.
The tax increases will also include an increase in the amount paid by businesses.
This includes an increase of the corporate rate from 30% to 35%.
In the past, businesses were taxed at a rate of 20% and it was only tax levied on profits.
The new system will apply to profits from both profits and sales.
The increase in taxable income will make Ireland the highest taxed country in the EU.
It will also have an impact on other major businesses, with a number of banks and companies expected to face increases.
This comes as the Irish economy recovers from the worst economic downturn in more than three decades.