"People were discovering what they thought were counterfeit bank notes but when we looked at photographs of them, it was clear to us that, actually, these were genuine bank notes with a little bit of wear on them.
"In some cases, people had been scraping the bank notes with a coin and that showed plastic underneath, which is exactly what it should do."
He has reminded people that people should not be scraping or damaging bank notes with a coin because it is illegal.
Distinct security features are present in real notes, he said.
"So for instance, the notes with the larger windows on them, there's a little bird in the corner. If you tilt the note, there's a sparkle that moves up and down the bird. The windows in the notes, whether they be older or the newer notes, they've got embossed or hologram features in them which are easy to tell."
Northcote said the polymer notes are durable, compared to counterfeit paper notes.
Plastic can show through if a real note is a little worn, whereas fake paper notes would simply tear.
Northcote said counterfeit money in New Zealand is rare and simple feel and look tests should identify whether a note is real.
"New Zealand has a really low level of counterfeiting by international standards and that's because our notes are so good. They've got lots of security features. None of our security features have been successfully defeated or replicated by any forger."
Reserve Bank tips on counterfeit notes
• Inside the large clear window is a hologram featuring a fern and a map of New Zealand. It also contains the same bird featured on the left-hand side of the note. There is also an embossed print denomination below the hologram.
• Polymer notes and their inks are water resistant. There should not be any blotches or running of the inks.
• Tiny micro-print of the note denomination should be visible with a magnifying glass. On the large numeral, the letters "RBNZ" are in microprint. On the front of the note, the foil inside the window reads "RBNZ 10 TE PŪTEA MATUA 10". On the back are the numbers "10101010 ..." and "RBNZ", between New Zealand and Aotearoa.
• Polymer notes have raised printing, which can be felt when you run your fingers over it.
• Each note has an individual serial number printed horizontally and vertically and these numbers match exactly. If the serial numbers are missing, or if you have several notes with the same serial number on all of them, some or all of those notes could be counterfeit.
• Most commercial papers used in forgeries glow under an ultraviolet light, but the Reserve Bank notes use special inks which look dull except for specific features that glow brightly. For example, the front of each genuine note includes a fluorescent patch showing the denomination.
• All images should appear sharp and well defined - not fuzzy and washed out.
• The colour of the bird changes when the note is tilted, with a rolling bar going diagonally across.
• When the note is held up to the light irregular shapes on the front and the back of the note combine like puzzle pieces to show the note's denomination.
• Polymer notes are tough, but most counterfeits are only paper. Moderate force should not start a tear in the note.
• If you believe someone is trying to pass you a counterfeit note, do not accept it, and notify the police. If you find you've already received a counterfeit note, put it in an envelope to avoid handling it further and take it to the police.