The elite department's Christmas shutdown is also safe from the chop under the new pay offer of 1.5 per cent a year over three years, unveiled on Wednesday.

But that is not all. All departmental allowances will be boosted by 2.5 per cent and the agreement front-loaded for Finance's 1800 public servants who have not had a pay rise since June 2013.

All they have to do in return, according an all-staff bulletin sent by Departmental Secretary Jane Halton, is move out of their crumbling office in the John Gorton building and into swanky new offices on Canberra Avenue.

Ms Halton said her public servants would be able to read fine print of the offer "shortly" after discussions with the Public Service Commission.

The fine print of the deal struck between the department and property developer Willemsen Group for the new 20,000-square-metre building at 1 Canberra Avenue is being kept a secret by Finance but the department insists it is a good thing for taxpayers.

Workers across the 160,000-strong Australian Public Service are facing longer working hours and the loss of time-off or leave entitlements if they are to get a pay rise in the current round of enterprise negotiations.

But the Finance boss told her troops on Wednesday they had no such worries.

"As you would be aware, any salary increases must be funded through productivity offsets. Our two main contributors to these offsets are savings resulting from changes to the organisational structure since January 2014, along with the anticipated productivity gains associated with the transformation program, including the move to a new building," Ms Halton wrote.

"As a result, other productivity measures that had been discussed, such as working an additional six minutes a day, and removing the Christmas shutdown period, are no longer required."