It's estimated €620 million in overpaid tax is yet to be claimed from Revenue.
Taxback.com says the money dates back to 2019, and estimates a surplus of up to €300 million was recorded for 2021 alone.
Analysis by the accountancy firm also shows the value of tax refunds increased by 74% between 2020 and 2021 to an average refund of €1,880.
CEO of Taxback.com, Joanna Murphy, says PAYE workers could be due a tax refund:
"Generally people that are PAYE workers don't expect to get tax back, they think that their payroll department take care of all of that. They simply look at what comes into their bank account at the end of the week or the end of the month and think that everything is taken care of. Anybody that's had medical bills, dental treatment, that have children in college, perhaps that a loved one in a nursing home, there's a hundreds of different tax reliefs and refunds and rebates are available to everybody in the state."
