The Housing Executive has issued an amnesty for people who are cheating the system.
Tenancy fraudsters using low rent housing to which they are not entitled have a month to hand in their keys.
Some people cheat by illegally subletting the houses or using them as "dole drop" addresses so that they can access benefits.
A BBC Spotlight report found that many of the properties were lying empty.
This was at a time when about 40,000 families in Northern Ireland were officially listed as homeless.
The executive said fraud unfairly deprived someone of a home.
Colm McQuillan, director of housing services, said: "Social housing is a valuable resource in Northern Ireland with demand far exceeding supply.
"By committing tenancy fraud, a family in need is wrongly and unfairly being deprived of a home.
"The majority of our tenants are lawfully living in their homes but some may not be. I'd encourage anyone who is not to hand in your keys during May's key amnesty."
Northern Ireland's housing associations are also offering the amnesty which operates for the month of May.