New Zealand stocks gained, led by local lender Heartland Bank for a second day as its rival Australian-owned banks faced new deposit levies across the Tasman, while Comvita extended its decline.

The S&P/NZX 50 Index rose 12.08 points or 0.2 per cent to 7,424.20. Within the index, 30 stocks rose, seven were unchanged and 13 fell. Turnover was $207 million.

Heartland Bank led the index higher, added 3.4 per cent to $1.81. The New Zealand-owned lender has the widest net interest margins among local banks as it eschews much of the mortgage market for more profitable, but riskier, business.

Its larger Australian rivals, which dominate the mortgage market, are facing increased regulatory costs and on Tuesday the Australian federal government announced a deposit levy across the Tasman.

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A2 Milk added 1.9 per cent to $3.67. Units in the Fonterra Shareholders' Fund rose 1.7 per cent at $5.99 after Fonterra Cooperative Group announced a higher forecast payment for Australian suppliers in the 2017/18 season than for the current season.

Retirement and aged care operators were mixed, with Summerset Group up 1.4 per cent to $5.04 and the recently listed Oceania Healthcare climbing 5.1 per cent to 82 cents.

Ryman Healthcare, the biggest listed retirement village operator, slipped 0.6 per cent to $8.43.

"We have seen a bit of a bounce in the retirement sectors," said Brad Gordon, investment adviser for Hobson Wealth Partners. "Summerset is up after being quite weak of late and Oceania has bounced after a fairly lacklustre opening," he said.

Gordon said the index was also supported by Chorus, which added 1.3 per cent to $4.64 and remains in favour after joining Australia's benchmark S&P/ASX 200 index.

On the downside, Auckland International Airport fell 1.6 per cent to $6.86, and Gordon said the stock was weighing on the index, and likely driven by some offshore flows.

"Overall, the airport story remains very, very strong."

Comvita continues to struggle, falling 3.6 per cent to $5.88 in the biggest decline on the benchmark index as investors continue to fret about the potential impact of the myrtle rust fungal plant.

Gordon said there could be some buying interest around these levels and the stock may be oversold given there wasn't any evidence that the situation is dire.

Xero rose 1.6 per cent to $21.85 as investors take positions ahead of its results today, while Z Energy, which is also reporting today, added 0.4 per cent to $7.83.

"The market will be looking out for margin trends," Gordon said.

The property companies are still garnering "a wee bit of a bid" as they are "very much a yield play", he said. Goodman Property Trust increased 0.4 per cent to $1.22, while Property for Industry gained 0.3 per cent to $1.61. Stride Property advanced 1.2 per cent to $1.75.

New Zealand's Reserve Bank is due to publish its monetary policy statement today. Economists are widely expecting rates to remain on hold at a record low 1.75 per cent but will be watching its forecasts closely to see when it expects to begin lifting rates.