Sir Michael says while the deal hasn't been signed, sealed or delivered yet, the company wanted to be proactive in announcing it.

He believes the agreement would secure the long-term future of Kiwibank, and it is time to broaden the bank's support within the wider public sector.

Sir Michael wanted to make clear that the proposed sale "is not some move to partial privatisation".

He hopes it can be completed before the end of the current financial year. Though if it doesn't go through, Sir Michael says it won't leave Kiwibank in dire straits.

"Kiwibank is not in distress at all; it will be much more constrained about its capacity to grow."

Sir Michael also had a word of warning for those thinking about taking their money out of Kiwibank.

"I should emphasise before anybody rushes to get their money out of Kiwibank, Kiwibank is an extremely sound bank. I have all my liquid assets in Kiwibank, other than my house and my car -- the only other major assets I have. I'm a very nervous, insecure, elderly investor and I'm not going to be withdrawing a single dollar.

"None of the Australian banks have a guarantee of that sort at all."

He admits the post side of the business is struggling, and the proceeds from the deal will help it invest in its core parcels and packages business and to pay down debt.

It is also anticipated a special dividend would be paid to the Crown.

Neither ACC or the Super Fund will be able to sell shares outside the existing shareholder base for five years.

Should problems come out of due diligence, the deal may need to be renegotiated in terms of price or other terms or the agreement could not go ahead.

NZ Post initially discussed the proposal with the two Crown-owned enterprises and approached the Government for permission to explore the idea in 2014. Active discussions were started by NZ Post early last year.

State-Owned Enterprises Minister Todd McClay says while the proposal could benefit the parties involved, it still needs to "stack up" before it goes ahead.

Newshub.