Since December 1, new limits have applied to interchange fees, which a retailer's bank pays to a shopper's bank when they use a card.
This means savings for businesses but Consumer NZ spokesperson Jessica Walker told RNZ's Midday Report today her organisation was worried it was not always flowing through to savings for shoppers.
People should not pay more than 1.2% or 1.3% in surcharges now, she said.
"Anything close to 2 percent is likely to be excessive. We want consumers to be on the lookout."
New Zealand's guidelines required retailers to offer shoppers a way to pay that did not incur a surcharge, such as cash or inserting or swiping a card she said, and people who were worried they were going to be charged too high a surcharge should use a different payment method.
"If you see a fee of 2 percent or more, swerve it."
There were also cases where surcharges were not appropriately disclosed, and shoppers should ask the retailer whether there would be a surcharge and how much it would be, Walker said.
Consumer NZ was "always" getting complaints about excessive surcharges and had not seen a change in that yet. Some businesses might not have updated their systems, she said.
"We're wanting people to be aware of this. Businesses are going to be saving money. We understand the fees are now comparable with some of the lowest in the world, so it's only fair that the saving is passed on to consumers."
Walker said estimates were that New Zealanders were paying anything from $45 million to $65m a year in excessive surcharges.
"Anything that can be done to protect consumers is a good thing. This is something we want to bring to the public consciousness if they are spending more over coming weeks and months."
Meanwhile, it has been reported that retailers want to push the government to ease its plans for a hardline ban on in-store surcharges.
"Our members have been really unhappy about it. We've surveyed all our members and we've been talking about it for a while and they're really clear that it's not something that they support," Retail NZ chief executive Carolyn Young said.
She hoped to convince the government to compromise by capping surcharges instead of banning them entirely.
"What we're trying to do is provide a solution that's a middle ground that should appease everyone."
Her proposal was for surcharges on debit card transactions to be capped at 0.5% and for credit cards to be capped at 1%.
