Christchurch ratepayers may be able to legally challenge rates bills from the past nine years because mistakes were made in the way they were set.
It has been revealed the resolutions voted on by councillors to set the rates haven't included the right wording around due dates and penalty payments.
The mistake was discovered by the Department of Internal Affairs and council staff are now writing a report for councillors on the legal ramifications.
Acting chief executive Jane Parfitt said on Tuesday this year's rates will be voted on again at the end of August, but information is being sought on how to correct the resolutions passed in previous years.
Ms Parfitt said legal advice is being sought on whether ratepayers would have grounds to challenge the legality of the rates they have been charged for the past nine years.
She will travel to Wellington on Friday and meet Internal Affairs staff to discuss the problem.