The average amount of tax people are claiming back from Revenue has increased to almost €1,900.
It comes as the cost-of-living crisis prompts more people to reclaim money they are owned.
Men are more active in claiming refunds than women, and for higher amounts, according to a survey by claims specialists Taxback.com.
The average tax refund has increased by more than €700 in recent years, and is now €1,888.
Recent figures obtained from a Dáil question by Sinn Féin finance spokesman Pearse Doherty revealed hundreds of thousands of taxpayers have overpaid tax.
The figures showed Revenue admitted €300m was overpaid by 450,000 taxpayers in 2021.
About €620m was overpaid in 2019.
Taxback.com said between the end of 2020 and the end of 2021, the average refund claimed by its clients amounted to €1,880. This was up from €1,076 in previous years.
Medical expense tax refunds were found to be the most common relief claimed last year. The average refund for men last year was €490, compared with €470 for women.
Chief executive of Taxback.com Joanne Murphy said: “Although we are only halfway through the year, 2022 has already seen record levels of inflation jumping to a 40-year high and hitting the pockets of Irish households hard.
“Most of us are looking to tighten our belts in one way or another. And yet, in the last few weeks, we learn that 450,000 people overpaid a total of €300m in income tax in 2021.”
Ms Murphy said going back to the last year in which people can still claim, Revenue records reveal since 2019 some €620m has been overpaid.
Aside from medical expenses, expenditure items people claim back on include tuition fees, flat-rate expenses and working-from-home relief.
Ms Murphy said: “The reality is that we’re really not great in this country for claiming the reliefs and refunds owed – which is a shame because many households throughout the country could really benefit from that added cash injection.”
She said many people are still unwilling to apply for a tax refund possibly because they believe is a difficult process or hassle.
“But the reality is it is very straightforward, and only requires a little prep in terms of keeping receipts or following up with your health practice or dentist, etc, to obtain the ones you don’t have.”
Ms Murphy encouraged everyone to take greater stock of their financial well-being and ensure they are not overpaying in tax.
Revenue is writing to taxpayers who may have overpaid or underpaid tax in these years, inviting them to submit returns to finalise their tax position.
In the past month Revenue has written to more than 50,000 PAYE taxpayers.