The RBNZ is ending March with fat balances from its depositors. They have been substantial for many months now.
These balances are known as Settlement Cash. And they pay interest on them, at the OCR level.
The owners of these balances are the Government (Treasury) and the banks.
These balances have swelled sharply as a result of outsized fiscal and monetary support policies during the pandemic.
But when the OCR interest rate rises fast, the amount of interest being credited to these account holders has been turbocharged.

When the OCR interest rate was just well under 1% in 2020 when these balances started to rise quickly, the amount of interest was hardly significant.
But the combination of very fast rising balances (now $48.5 bln) and a fast rising OCR (now 4.75% from a rising trend that started in mid 2022) has turbocharged these interest payments by the RBNZ to its depositors.
It is hard to see these balances receding now that the 'reservoir' has been filled. It could (and probably will) recede if the economy stays positive. But that is a brave assumption at this point in the economic cycle.
And that means, if the OCR rises to 5% next week, and the Settlement Account balances stay over $48 bln, that annual cost will keep on rising to about $2.4 bln (from the $1.7 bln in the chart above).
Settlement cash balances are funds used to settle transactions between financial institutions. When one bank owes money to another bank, banks will use settlement cash to settle the transaction. Settlement cash can also be used to settle transactions in other financial markets, such as the foreign exchange market.
The Reserve Bank plays an important role in managing the country's payment and settlement systems, and settlement cash is an important tool for ensuring that these systems operate smoothly and efficiently.
Settlement cash balances can rise quickly due to several reasons involving the economic cycle.
If lending activities decrease, banks and financial institutions will have more cash on hand, leading to an increase in settlement cash balances. Reserve Bank policies can also affect settlement cash balances. For example, when they buy securities for financial stability reasons or lower interest rates, that would increase the amount of cash in circulation. And economic uncertainty plays a role too. If there is economic uncertainty, banks and financial institutions may hold more cash as a precautionary measure, which would result in an increase in settlement cash balances.
None of these reasons suggest settlement cash balances are about to decline significantly. And there is little expectation the OCR is about to be cut. So, so long as the RBNZ pays the OCR rate on these balances, the cost to them will be high. And you have to wonder, in a recessionary or low growth period, perhaps earning 5% on these balances at no risk is better than lending. Certainly high earnings on settlement cash balances will encourage banks to be very conservative in their lending policies.
Not that this final observation is anything more than a thought-experiment, but if the banking system can make $2.4 bln (before tax) on these balances, that would represent $1.7 bln after tax, and a quarter of their 2022 tax-paid profits.
Finally, it is probably worth pointing out that at 4.75% the current OCR that the RBNZ is paying its depositors, Treasury pays Kiwi Bond holders only 4.25% for terms of one year and longer. The RBNZ paying +50 bps more (also for zero risk) is a premium Kiwi Bond holders would love access to.

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