Lower Hutt woman Tina Beznec set up the Trade Me auction "YOUR tattoo on my Bum!!" after twice being made redundant in the last year.
Bidding for a 9cm by 9cm space on her buttock on Saturday had reached $10,900, with the auction due to close next Friday.
She plans to give 20 per cent of the winnings to a charity of the winner's choice.
About 10 auctions were also on Trade Me on Saturday, for tattoos on bottoms, a back, an arm and a leg.
The sellers also say they will give between 20 per cent and 100 per cent to charity.
Bids ranged from $14.50 for a woman saying she will wax any part of her body to $1500 for a tattoo on both buttock cheeks to raise money for a child with cancer.
Several auctions have not received bids.
Trade Me spokesman Paul Ford said Ms Beznec's auction was "borderline" - as body parts are on Trade Me's list of prohibited items.
It is keeping an eye on whether people thought it was a laugh or crossed the line, he told NZ Newswire.
Trade Me is also watching bids and has the ability to remove any that are not genuine.
The auction has so far reached almost $11,000 and been viewed almost 170,000 times.
Ms Beznec says her parent are proud of what she is doing.
The winner will get a framed photo of the tattoo,the chance to watch and the knowledge they have left their mark.
3 News/NZN