If the OCR peaked at 5.5 per cent, as forecast by the RBNZ, this payment would rise to $2.7b on $49b of reserves.
The RBNZ has never faced these costs in the past. Before Covid-19 prompted it to start printing money, it typically held $7b or $8b of bank reserves, or settlement cash.
A former Bank of England deputy governor, Paul Tucker, last month published a paper suggesting central banks could consider paying banks less interest on part of their reserves, provided the risks were managed properly.
This would save taxpayers money – possibly hundreds of millions of dollars a year in New Zealand's case.
Put to Finance Minister Grant Robertson, he said he hadn’t received advice on the issue, which was a matter for the RBNZ.
“The RBNZ has operational independence and its policy is to pay banks the OCR on their settlement balances. This approach is in line with other central banks,” Robertson said.
When put to RBNZ deputy governor Christian Hawkesby, he said paying banks less interest on part of their reserves could hamper the RBNZ’s efforts to lift interest rates to cool inflation.
Hawkesby was aware of Tucker's work but said the RBNZ wasn't "actively" considering changing its policy.
He worried paying banks less interest while trying to get them to lift their mortgage and deposit rates could complicate things.
He said the RBNZ’s priority was to lower inflation, in line with its mandate, and “the way that we’re doing things at the moment gives us the best chance of doing that”.
Hawkesby said that if the aim of paying banks less interest on some of their reserves was to effectively tax them more, then that was a matter for the government to consider.
Nonetheless, Robertson didn't want to get involved.
He didn't buy the argument that the rising interest costs the RBNZ faces have become his problem, because the RBNZ can't cover these on its own.
Indeed, the RBNZ has started drawing down on a Crown indemnity, provided by Robertson, to cover any losses incurred by its main money printing programme – its Large-Scale Asset Purchase programme.
Hawkesby isn't alone in worrying that making banks wear some of the costs of money printing could hinder the RBNZ's efforts to cool inflation.
His concern is shared by former RBNZ deputy governor Grant Spencer, who is now an adjunct professor at Victoria University, and former RBNZ assistant governor John McDermott, who heads up Motu Research.
As reported last month, McDermott said it would be too risky for the RBNZ to try to reduce the cost of the problem, which he believed it created, by doing something "cute" with the interest paid on banks' reserves.
However, Michael Reddell – a former senior staffer at the RBNZ – was of the view that provided the RBNZ paid banks the OCR on a large enough portion of their reserves, making the change wouldn't hinder its efforts to get banks to lift interest rates.
Indeed, banks need some reserves to keep the financial system liquid, so that transactions between banks can be settled.
Furthermore, Reddell noted tiering interest rates paid on bank reserves has been done before by the European Central Bank and Bank of Japan.
While he believed this would be workable, he opposed singling out banks and effectively taxing them more. He didn't think they were making windfall profits.
Nonetheless, if the Government believed banks should pay more tax, Reddell suggested it lift the corporate tax rate.
Banks' profits have been rising to record levels in dollar terms.
Their net interest margins have also been climbing this year to levels above those pre-Covid. Net interest margin is an indicator of how effectively a bank uses its funding to generate revenue.
The country's two largest banks – ANZ and ASB – had net interest margins of 2.3 per cent and 2.5 per cent respectively in the September 2022 quarter. This was up from 2.0 per cent (ANZ) and 2.2 per cent (ASB) in the September 2019 quarter.
However, banks’ returns on equity are back to pre-pandemic levels. Return on equity is an indicator of how efficiently a bank uses shareholder funds to make profits.
