The month-long amnesty comes ahead of Wiltshire Council's crackdown on tenancy fraud.
A council spokesman said the cost of placing a family in temporary accommodation is Â£18,000 a year and the fraud stops genuine people in need.
Those found guilty of tenancy fraud can face up to two years in prison.
"They also risk an unlimited statutory fine and will have to pay back any profits they have made," the spokesman said.
"Social housing tenants may be prosecuted for not occupying their home as their main residence and illegally subletting parts or the whole of their home.
"Anyone who returns their keys at reception at the Wiltshire Council offices in Salisbury or Trowbridge before 10 February will not face legal action," he added.
At present there are more than 17,500 social housing properties in Wiltshire, with 5,319 of those owned by Wiltshire Council.
People illegally subletting their council-provided homes are being offered the chance to hand in keys with "no questions asked".