Singer Rihanna is in trouble after she was caught working as a tattoo artist without a licence to do so.

The 21-year-old was spotted wielding a needle in Manhattan parlour East Side Ink Wednesday night and she etched umbrella designs and the letter R on three resident artists.

Contactmusic.com reports that the session could end up costing her dear, because tattooists need a licence to hold a needle in New York.

Rihanna could be fined almost $2,000 for the three misdemeanour offences.

"Only licensed tattoo artists can administer tattoos in the city according to the City's Health Code. We are sending someone down to follow up on this," said a New York City Health Department spokesperson.