The emergence of an accounting error means that the Republic's general debt is 2% or €3.6bn (£3.1bn) lower than previously thought.
The double counting error occurred when the National Treasury Management Agency (NTMA), which manages the country's debt, and the Housing Finance Agency (HFA) both put loans to the latter on their accounts incorrectly.
However, while the correction is good news on Ireland's general debt figures it will not reduce the size of the expected budget adjustment of over €3.6bn or targets as set out in the EU/IMF/ECB agreements because it is not classified as national debt.
Loans direct from the NTMA to the HFA should appear on the agencies' respective accounts as assets, or liabilities.
The department said both the NTMA loans and the HFA liabilities had both been recorded as part of general Government debt - effectively a double count.