The desks at Tunstall, Stoke and Chasetown police stations will close by the end of October. Six other inquiry desks will have their hours cut.
The force said some of the reductions would be achieved through voluntary redundancies and other workers would be deployed elsewhere.
Unison said fewer workers would be affected than originally feared.
Police and Crime Commissioner Matthew Ellis said the force's priority was frontline policing.
"There will still be ample face to face counter services including the ability to formally present documents and other legal requirements, just not quite as many as there are now," he said.
The inquiry desks at Hanley, Longton, Tamworth, Cannock, Stafford and Burton will have their hours cut.
Unison branch secretary Susan Wall said the decision followed a one-year review of the force's estates.
"It was always mentioned some desks would close," she said.
"We thought it could be more. We have had more staff indicate they want to leave than we are going to lose."
Three Staffordshire Police inquiry desks will close and 28 posts will be axed in a bid to save the force money.