More than £2.2million is to be transferred into the next financial year for the refurbishment of Ladywell House in Newtown by owner Powys County Council.
The council's cabinet is expected to give the go-ahead to the move at its meeting on Thursday.
It follows delays to the refurbishment of the office building which means completion is not expected until August this year.
"The Project Board has accepted a revised project completion of August 2019," says a report to cabinet.
"This is a result of design delays and the need to fit windows in spring/summer. We therefore need to roll money forward to cover the works."
Ladywell House was purchased by the county council from the Welsh Government.
The Welsh Government has offices in the building while other offices are occupied by a mixture of private and third-sector businesses and organisations.
