The Inland Revenue Department is closing its Upper Hutt office to allow earthquake-strengthening work to be carried out.
The department received a preliminary assessment on the building earlier this week which stated it needed urgent strengthening.
IRD commissioner Bob Russell says the closure affects about 250 staff.
He says the department is still working out where those staff will go but IRD's Wellington office could accommodate some of them.
Mr Russell says the building could be closed for about a month while the work is done.