A Mangawhai resident is questioning whether targeted rates set by the Kaipara District Council for the EcoCare wastewater scheme "comply with the law".
The council is defending  its rating process, but is having the issue investigated.
Clive Boonham, a retired lawyer who has lived in Mangawhai for the past 18 months, said he believed because of non-compliance issues, the targeted rates levied over the past three years were invalid and should be refunded.
According to the Local Government rating act of 2002, targeted rates can only be levied on a service,"if that service is connected or available as at the end of the rating year, immediately before the rating year for which the rates are set", Mr Boonham said.
If his allegations prove correct, Mr Boonham said the only way forward for the council to reset the rates would be through validating legislation by Parliament.
Using the 2008-09 year, which starts  on July 1, 2008, by way of explanation, Mr Boonham said the EcoCare service had to be connected or available by June 2008. He says this was not the case. The scheme did not become operational until October 2009, rendering rates invalid for the 2009-2010 year.
 The council did credit Mangawhai ratepayers to the tune of $158,332.18 on the annual EcoCare rate for the 2008-09 year, but not the one-off rate which attracted a Government subsidy.
To date it had not refunded the 2009-10 annual or one-off rates.
Mr Boonham says the council was not entitled to levy a rate when a service was connected part-way through the year.
"The Rating Powers Act of 1988 did allow for such circumstances, but this was repealed and replaced by the new provision in the Rating Act in 2002.
 "Every document in the rating process chain is defective and as a result the EcoCare rates from 2008 until 2011 are invalid."
Finance manager Mike Fleming said any rating charge was made on the projection that the service would be available - if this was not the case those affected would have credits made on their  rating statements.
 "This process requires a lot of work and staff are still processing eligible credit entitlements."
 Kaipara chief executive Jack McKerchar said: "While the council is confident it has acted legally, it is having Mr Boonham's queries investigated."