A spokesman said that since the project was rolled out over 2013/14, average sick leave taken each year had reduced by nearly two days a person.
"This has resulted in productivity savings to the taxpayer of $3 million each year. The project has also resulted in a healthier workplace, with a range of initiatives undertaken such as physical improvements to IR workplaces and making free onsite annual flu vaccinations available."
One of the "elements" in the initiative was the "welcome back conversations which our people leaders are encouraged to have regularly with staff following any period of sick leave".
"These conversations are tailored to the situation and nature of the absence. This can range from a quick informal chat to ensure the staff member is well enough to be at work, if action is needed by IRD to help keep the staff member well and to let the staff member know about any work they may have missed, to a more in-depth discussion if the manager has any concerns about the frequency or length of sick leave being taken."
Inland Revenue staff were encouraged to be open and honest about their sick leave, and to adhere to guidelines for taking it, the spokesman said.
But employment law expert Claire English, of law firm Chen Palmer, said it was the first time she had heard of such an initiative, labelling it "interesting" and "unusual" and saying it "seemed to step a little bit closer to the line than you usually see policies doing".
"I could see from the employee's perspective of course it's a waste of time, especially if you've just had a stomach upset or the flu, which is what most of us go out for really, and it also does potentially raise the question of why, in the sense of, is this a trust issue?"
Mrs English said it was well understood that the Holidays Act had a default provision stating employers could require a medical certificate after three days of sickness, but they could require one earlier "where they have reasonable cause to suspect that something's up".
"It's a privacy issue too. How much information about what can sometimes be quite personal matters do you need to disclose and what is the employer going to do with all this information?"
Mrs English said most employers followed the guidelines under the Holidays Act, allowing the first three days to take effect.
"The employee has no choice [to attend] and make a judgment call as to where to draw the line - I think there is a line there and I do think they're coming right hard up against it and it puts both sides in a tricky position."
One IRD worker said they felt the whole process was a bit intimidating and a waste of not only their time but also their manager's.
A more senior staffer believed it wouldn't affect them as much and felt if they had to take a sick day, their superiors would appreciate that they were actually sick.
A Ministry of Business, Innovation and Employment spokesman, said it couldn't comment on individual cases, but the general rule was that employers were able to ask for proof of sickness or injury at any time once an employee took sick leave.
A spokeswoman for the National Union of Public Employees [NUPE] said although she couldn't comment specifically about Inland Revenue, her organisation had noticed a "tightening up" of sick leave in the public sector.
But she said holding a meeting after an employee had one day off sick was "ridiculous".
"I would have a concern being called in after one day. That doesn't seem reasonable and probably not really creating good workplace relations, to be honest - unless there was a very good reason, like they were demonstrating they had concerns around a pattern [of behaviour]."
She said wellness meetings were also held in the Ministry of Social Development.
