The Stanwell Park 10-year-old may have been the only Archibald Prize contender whose mum took him to deliver his work last week as entries to the historically controversial competition closed.

His self-portrait now awaits judging at the Art Gallery of NSW alongside likenesses of convicted drug smuggler Schapelle Corby, boxer Danny Green and cricketer Adam Gilchrist.

If chosen to progress, Lachlan will usurp a 15-year-old Rolf Harris as the youngest known competition finalist. But he is keeping cool about his prospects of taking home the $50,000 first prize.

"You have to paint a picture of some person, like you, or somebody else you know somehow," is how Lachlan explains the competition rules, which indicate a preference for subjects known in the fields of art, letters, science and politics.

"I hope I win, but it doesn't really matter."

Lachlan discovered the Archibald as the competition concluded last year.

Home-schooled, he set about creating his own entry as part of art classes led by his mum, Lucinda Coleman.

"He saw the Archibald in the newspaper last year and he's been drawing and painting ever since," Mrs Coleman said.

"He's very good at drawing Prime Minister Kevin Rudd."

There were 849 entries in this year's Archibald. Between 35-40 will be announced finalists on March 26.

The Art Gallery of NSW website lists Rolf Harris, in 1946, as the youngest known entrant.

However, a gallery spokeswoman contacted by the Mercury said it was impossible to confer the title because entrants weren't asked their age and it didn't become evident unless their work made the competition final.