"As you would appreciate, the cost of capital, whilst not the only driver, is a material input cost of doing business," Hiddleston says.
"Like most businesses, significant increases in material input costs generally lead to an increase in prices for customers," his letter says.
In the wholesale market, the two-year swap rate has dropped about 30 per cent from 2.31 per cent in April last year to 1.62 per cent currently.
"In the immediate future, we intend to await the outcome of the May official cash rate determination from the RBNZ before we decide what movement, if any, there will be to interest rates on our agri loans," it says.
"A reduction in the OCR could assist in the near term in absorbing capital costs that would potentially otherwise need to be passed onto our agri customers. We'll let you know if this first development impacts you."
The OCR decision and monetary policy statement will be delivered on May 8. While some economists are expecting an OCR cut, ANZ's own chief economist, Sharon Zollner, expects the central bank to hold off until August.
In May last year, the Reserve Bank revealed the results of a benchmarking exercise it set the four major banks, ANZ, ASB Bank, Bank of New Zealand and Westpac, asking them to report on how much capital they would need to support a hypothetical portfolio of loans to 20 dairy farms.
Each of these banks uses its own internal models for calculating its risk-weighted capital requirement to meet regulatory minimums.
The other smaller banks in New Zealand – the big four account for about 88 per cent of New Zealand's banking system – are forced to use standardised models which means they have to hold more capital proportionately and are therefore competitively disadvantaged.
While the central bank didn't name which bank produced which outcome in the dairy portfolio test, it found an extraordinary 40 percentage-point difference between the highest and lowest average risk-weights among the big four.
"The provisions results show significant variation in model outcomes, even for the same level of underlying risk," the Reserve Bank said at the time.
It was this huge disparity that was one of the factors that fuelled the higher capital proposals the central bank is currently consulting on – the consultation period is set to close on May 17.
The proposals include a near doubling the minimum tier 1 capital, or equity, each of the big four banks has to hold from 8.5 per cent to 16 per cent. The benefit they get from using their internal models will also be reduced to 90 per cent of the results the standardised models produce.
Currently, banks on average have about 12 per cent of risk-weighted tier 1 capital.
The Reserve Bank is proposing a five-year phase-in period for the change. ANZ's letter is the first public indication that any of the banks have been forced to increase capital earlier, even under the existing rules.
In February, the Reserve Bank released information showing that ANZ currently has to hold just over half the capital that government-owned Kiwibank is forced to hold to back every $100 of mortgage lending.
Nevertheless, the Reserve Bank has approved the models ANZ has been using from 2008. So while ANZ may have been extracting maximum benefit, it is clear that it has not flouted the rules.
Hiddleston says the impacts from the central bank's capital proposals "are likely to be significant on those customers borrowing money who are involved in the property, commercial and agri sectors" and suggests those customers should start planning for that.
"We think it is prudent to help you plan to reduce your debt as much as you can, restructure you facility limits or pay down where you may have credit funds elsewhere," his letter advises.
"You should also think carefully about your borrowing requirements in the near future, including factoring in potential increases in borrowing costs."
