Australia Post boss Paul Graham says more post offices will close, but won't say how many.
He claims the closure at Tharwa, south of Canberra, is not the national carrier's fault.
The high-paid chief executive told Senate estimates late on Wednesday night that he did not have a list of planned or recent closures.
"We do not have a list," Mr Graham told the late hearing.
"We have an indication of those we think are doing it tough ... And we keep a watching brief on those."
He took on notice a question of how many LPOs had closed, sought to hand back their licence, tried to sell or otherwise indicated they may not be viable, since July 2022.
Liberal senator and opposition communications spokesperson Sarah Henderson said it was "not good enough" that the chief executive could not answer.
"Post offices, particularly in regional communities are the lifeblood of those community," Senator Henderson said.
Mr Graham said two-thirds of licensees surveyed by Australia Post wanted to retire in the next three to four years.
He said that Australia Post was considering reactivating its previous licence buyback program to close down LPOs in metro areas assessed as being overserviced.
And Mr Graham said a "generational shift" was underway as licensees grew older and handed back their licences due to age or ill health.
The Canberra Times reported last weekend that Tharwa, south of Canberra, will no longer have a post office from Thursday, after the town's General Store sold and the vendor relinquished his licence.
It is understood that the new owner sought a new licence to keep operating the Tharwa LPO, but Australia Post refused, only offering to allow a community postal agent because banking services were not used frequently.
Senator Henderson demanded an explanation.
"Why did you refuse to issue Tharwa a new licence?" she asked the chief executive.
"The Tharwa post office has served its local community for 132 years."
Mr Graham said the closure was "not a decision of Australia Post" because the previous owner had "handed back his licence."
"Tharwa has 82 residents," Mr Graham said.
"We have seven transactions a week in that post office ... It's not an active business."
The chief executive claimed that "no one's interested in taking on a licence for 8 transactions a week."
"We have looked at alternatives but there is no one interested in taking on that business."
But it's understood that the new owner has requested a licence and wants to keep the LPO open, not accept a licence for it to be a community postal agent.
Residents of Tharwa and the surrounding region, many living on rural properties, have relied on the post office to pick up parcels, which the postie does not deliver to their doors.
LPO licences are held in perpetuity and can only be transferred to a new owner with Australia Post's consent.
They are significantly more expensive for Australia Post, which pays licensees tens of thousands of dollars a year to operate LPOs, compared with CPAs - which Mr Graham said "run a very narrow range of services".
"The CPA works well in a very small town where there is not a requirement for services other than mail or parcels," he said.
Australia Post is a corporate Commonwealth entity and governed by the Australian Postal Corporation (Performance Standards) Regulations 2019.
The regulations require Australia Post to operate a minimum 4000 retail outlets nationally, with at least half and no fewer than 2500 to be in rural and regional areas.
Its annual report says Australia Post has 4118 "retail stores" nationally, a figure that lumps together LPOs and CPAs.
Mr Graham said Australia Post was "absolutely committed to the viability of our licensed network, but we are facing a generational change due to the ownership of these post offices and also the way customers are interacting."
