It has been revealed that government bodies owed more than £4.5m in rates at the end of the last financial year.
Almost £2m of that was owed by NI Water, which was in dispute about how much it had to pay. It has said that it has now settled its debt.
Some of the overall figure was owed because bills were issued late following amendments from the previous year's figures.
The unpaid rates bill for the whole of NI was £157m at the end of 2009-10.
It had almost doubled in the previous four years.
DUP Strangford MLA Simon Hamilton, who asked the Department of Finance for the figures, said that public bodies needed to "tighten up" their procedures in light of the statistics.
He added: "At a time when government finances are under pressure, it is important that the public sector sets a good example by ensuring that money it owes is paid promptly."
A spokesperson for NI Water said that it had settled its bill through "a combination of corrections to the 2009/10 invoices and further payments".
She added: "Payment arrangements have been agreed with Land and Property Services for the 2010-11 rates bills."
The list provided by the Department of Finance also said that the Ministry of Defence still owes more than £800,000 in unpaid rates.
That is because of an ongoing dispute about the rateability of properties which have been vacated.
An MoD spokesperson said it was in "ongoing and productive discussions" with Land and Property Services about the figure.
Public bodies in Northern Ireland, such as government departments, health trusts and education boards pay about £140m in rates each year.
The Department of Finance said that it has a small team which works exclusively with public bodies.
It said the group had conducted a "thorough exercise" during 2009-10 to ensure all public body data was updated.
It added that this had proved effective in ensuring early payment of monies in 2010-11.