Dominic Cummings and his family have had a council tax bill that could total £50,000 written off.
Durham County Council bosses carried out an inspection of two homes built at North Lodge that confirmed they had been built without planning permission.
But the local authority said council charges owed on the properties have been waived due to the amount of time passed.
It is believed between £30,000 and £50,000 could have been owed in council tax.
Instead, charges started to take effect on the two properties from October 4.
Mr Cummings built his Band A cottage on the farm with his dad in 2002.
Following complaints from members of the public, a planning investigation was launched in June and found “historic breaches of planning and building control regulations” but council officials said no further action would be taken.
It came after the Prime Minister’s chief adviser hit the headlines for making a trip from London to County Durham during the lockdown after he and his wife suffered coronavirus symptoms.
John Hewitt, corporate director of resources at Durham County Council, said: “I can confirm that the Valuation Office Agency has concluded its inspection and provided us with details of the required changes to the valuation list in respect of North Lodge.
“The current single assessment will be replaced with three entries in the rating list going forward.
“These changes will be implemented with effect from 4 October 2020, which is the date we have been instructed to apply the changes from.
“The date from which the rating list is to be amended is a matter for the Valuation Office Agency.
“We are instructed that it has made its assessment in line with the relevant legislation and custom and practice in terms of such changes in accordance with Article 3 of the Council Tax (Chargeable Dwellings) Order 1993.”
