Further measures to rein in New Zealand's housing market might be needed, says the International Monetary Fund (IMF).
The Washington-based organisation has been assessing the resilience of the New Zealand economy in the event of a financial shock.
It has rated the country's banks as sound, and said the government's books were in good shape.
But mission chief Thomas Helbling said the Reserve Bank should have debt-to-income limits in its toolkit, just in case the housing market surged once again.
He said the IMF did not recommend deployment of the tool now, but did recommend deployment in the event that recent attempts to slow household growth were temporary.
Mr Helbling also recommended banks put aside more capital to protect themselves.
"The main concern is that the large banks feature very strong similarities in business models, with a very high concentration in mortgage lending and, to some extent, the dairy sector. And there's a significant reliance on foreign funding, Dr Helbling said.
"All these elements have a systemic risk to the sector which call, in our view, for higher capital requirements."
The IMF also again trotted out the usefulness of a capital gains tax, which it said would help divert investment into the productive sector.
"We would argue it's (capital gains tax) more something that would help at the margin," said Mr Helbling.
"There is a sense that (the) asset allocation of New Zealand households (puts) a bit too much emphasis on housing, rather than other investments."
At the same time the IMF was speaking, the Reserve Bank said it would review the capital requirements of banks.