“Feel” the note. There should be raised ink on the denomination of the note and the letters at the top.
“Tilt” it. A bright shiny bar should roll across the bird's silhouette on the front of the note and the holographic window's colours should shift and change, revealing fine details.
Polymer banknotes and their inks are water-resistant.
There should not be any blotches or running of the inks.
Each note has an individual serial number printed horizontally and vertically, and these numbers match.
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.