The Australian Tax Office is not softening on the timeline for its job cuts despite being asked to slow down its second redundancy round, in which almost another 2000 workers will go out the door between now and October.

The Australian Services Union, which represented about 1000 of the 20,000 ATO staff, said "pausing" the second round would reduce the need for forced redundancies afterwards.

But an ATO spokeswoman said a commitment had been made to staff to "minimise anxiety by completing the second round of voluntary redundancies as quickly as possible".

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"If the process were delayed there would be serious financial impacts for the organisation, which would require an even greater reduction in staff numbers," the spokeswoman said.

"The ATO has received a sufficient number of expressions of interest through the second round to meet our commitment to government to reduce the overall size of the ATO workforce by 3000 by October 31, 2014.

"We have aimed to reduce uncertainty for our staff during this process while managing the impact on the community."

The agency was due to lose 1300 staff in its first round and another 1300 in its second.

About 900 of the first-round redundancies were already complete and the rest from that cohort will be gone by August.

The 900 staff gone so far included 258 executive level-one staff, 183 APS6s and 118 EL2.1s.

The second round will be finished by October. 

The ASU's tax branch secretary, Jeff Lapidos, said pausing the second round would allow many workers to consider options such as job swaps, which allowed employees who wanted to stay to swap with a colleague who wanted to leave.

The redundancies were happening while the ATO was in the midst of bargaining over agreements affecting their staff's pay and conditions. 

Mr Lapidos said the ATO had attempted to get rid of provisions in the future agreement that would allow people facing redundancy to re-skill and be redeployed within the organisation where practicable.

The union official said it was the closest mechanism in the agreement to a no-redundancy clause.

The ATO's spokeswoman said the agency would not comment about negotiations as it was bargaining in good faith, except to say "we are discussing a range of employment conditions". 

"We have openly told our staff that we have discussed the redundancy clauses and that our bargaining discussions are ongoing," she said. "We are keeping our staff regularly informed and will continue to update them through the bargaining process.

"The ongoing reviews within the organisation are a part of reshaping the ATO in order to continue to deliver on outcomes in the most efficient and effective way.

"If any further staff adjustments are required, then they will be delivered by our normal business as usual processes including attrition and redeployment."