The Labour Party is calling for a promotional campaign to ensure that people who are not claiming their full tax allowances are aware of what they are entitled to.
"There are a startling number of people who are not aware there is money which belongs to them, that they are not claiming," Ms Joan Burton, Labour Party spokeswoman for finance said.
The figures released by the Department of Finance show that a significant proportion of people are not aware they can increase their tax credits. People who cannot afford it are losing out financially."
Figures released by the Revenue Commissioners show that only 60 per cent of tenants claimed the tax credit for renting in the private rented sector while a significant number of non-medical card holders, who have spent more than €125 a year on medical bills have not claimed the associated tax credit.
Tax credits are also available for trade union membership and for those paying the waste management charge.
"These tax credits remain unclaimed because people just do not know about them or believe the Revenue Commissioners will work it out for them," Ms Burton added.
"An extensive information campaign needs to be undertaken immediately.. These tax credits should be money in people's pockets - not saving the exchequer millions of euro a year."