Inland Revenue has confirmed details of a major restructuring after closing early yesterday.
The Public Service Association, the union that represents government workers, said it had "serious concerns'' for staff after IRD announced its final decision document on its proposed business transformation, which the union believes could affect up to 4000 staff in the organisation.
IRD shut its offices four hours early yesterday and closed its call centre for more than two hours after lunch so staff could hear about changes at the organisation.
PSA spokeswoman Erin Polaczuk said the document showed organisational changes would be made from next February, with the rollout of computer system changes beginning two months later.
She also said there was little transparency around possible reductions in staffing numbers.
"The loss of expert staff and the lack of certainty for workers reapplying for more simplistically modified roles means that important regulatory changes to the tax system rest on very shaky foundations.
"This could affect up to 4000 staff in varying ways at this stage of the restructure, and this has not been fully explained.''
Ms Polaczuk said the PSA understood there would be a 25% to 30% reduction of staff by 2021.
IRD said there would be no reduction in the frontline services staff in the organisation.
Commissioner Naomi Ferguson said 3300 "customer-facing'' staff would all be "offered new roles or confirmed straight into new roles''.
An IRD spokesman said those employees not confirmed straight into new roles might have to go through an application process.
IRD has also added 18 specialist positions across the organisation.
The department employed 5789 people as at June last year.
In March last year, IRD announced it would cut 1500 jobs "across the board'' between 2018 and 2021.
It said the workforce would shrink by 25% to 30%.
The transformation plan is part of a $1billion-plus modernisation of the tax system and the biggest change to the system in 25 years.
An IRD spokesman could not be reached for comment.
