It was billed as the next generation of banknotes – with improved security and top-to-bottom clear windows – but the numbers folk at the Reserve Bank missed one important step in the tech-heavy journey: spellcheck.

An anonymous tipster with eagle eyes, a magnifying glass and, presumably, a little free time, alerted radio stations to a typo on the new $50 banknote that has escaped everyone's attention since 46 million of them were rolled out in October last year.

A close-up of the spelling mistake. Credit:Triple M

The RBA has confirmed the word "responsibility" is incorrectly spelled "responsibilty" - without the third "i".

And it has admitted the error was brought to its attention back in December.