More than 600 tax workers will be affected as the ATO closes it offices in Sydney's Hurstville and Southport on the Gold Coast in about 12 months.

The Canberra Times revealed last week that the Tax Office had 4700 desks sitting empty in its properties around the nation.

Rumours of plans to rationalise its office network have left workers to fear they have to choose between moves to faraway offices or redundancies. The ATO is also looking at shedding 900 jobs in the next seven months as it struggles with government cuts to its budget. Commissioner of Taxation Chris Jordan announced on Tuesday that his office would not renew the leases at Hurstville, where 530 public servants work, and at Southport which has 77 workers, when they expire in 2015.

Mr Jordan confirmed what workers at Hurstville and Southport had long suspected, that their workplaces were to be closed down, with the commissioner saying the decision ''was a difficult one''.

''In making the decisions we looked at the cost of accommodation, the large number of vacant work points, costs of refurbishing and the availability of accommodation at other ATO locations, as well as broader issues such as our investment in new technologies and how this will change the way we work,'' Mr Jordan said.

''Given we required a smaller accommodation footprint in Hurstville we were unable to secure a lease arrangement that represented value for money.''

Mr Jordan said workers had time to make decisions before the tax offices shut down for good in late 2014 and early 2015. ''The closures are more than 12 months away, which gives people a good lead time to consider their options,'' the commissioner said. ''We will work with staff to relocate them to another ATO office.

''We will have people on site to answer questions and dedicated teams working with affected staff.''