The Wellington City Council's made another embarrassing blunder on ratepayer bills. Mayor Andrew Little's told Newstalk ZB ratepayers have been overcharged by about 10 dollars each - for the Greater Wellington Regional Council levy. He says it'll be rectified in the next bill. Last month, it was revealed the council had undercharged ratepayers by almost 3.5 million dollars for its sludge levy. Construction costs soared in building the city’s first sludge minimisation plant, meaning households needed to fork out between 3 dollars and 100 dollars each, with an average undercharge of 40 dollars per levy-payer. Speaking to Wellington Mornings with Nick Mills, Little this morning defended the council's Chief Financial Officer Andrea Reeves, insisting she's still doing a great job. He says she recognises the problem and has independent people coming in and telling her what has led to the mistakes. Little says he's revealed this second blunder out of full transparency. "Part of [being mayor] it is about changing the culture of council, and getting those things ironed out," he says." But also when things do go wrong, let's just step up and say it, and fix it, and trying to do that." Reeves previously apologised for the sludge levy error, saying to prevent this happening again, stronger internal controls and review steps had been put in place. The Greater Wellington levy funds regional services like biosecurity, flood protection and regional transport. The Wellington City Council is apologising for the second accounting error, but says it means ratepayers will pay less than previously thought. It says it's confident all rates assessments are now correct.