About 46 million A$50 currency notes in Australia have an embarrassing typographical error that was overlooked by the central bank before they were printed and circulated.

The mistake first became known today.

A listener to radio broadcaster Triple M sent it a magnified photo of the Reserve Bank of Australia's (RBA) new A$50 note highlighting the word "responsibility" misspelt as "responsibilty" three times.

The note is Australia's most widely circulated, accounting for nearly half the total value of other banknotes in use, the RBA says.

It went into circulation on October 18 last year, incorporating new security features to deter counterfeiting and tactile elements for the visually impaired. 

It carries a headshot of Edith Cowan, the first woman elected to an Australian legislature from 1921 to 1924.

The typo appears in an excerpt of Cowan's maiden speech to Western Australia's parliament featured on the note.

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The quote, repeated over the banknote, reads, "It is a great responsibilty (sic) to be the only woman here and I want to emphasise the necessity which exists for other women being here." 

The central bank is aware of the error, a spokeswoman said. 

"These banknotes are legal tender and can continue to be used as normal," she said.

"It does not affect their validity or functionality in anyway and we will correct the spelling during the next print run," she added.