Christchurch City Council says it has a plan for dealing with refunds it may owe ratepayers for late fees they were mistakenly charged for the past nine years.
Since 2004 the council's rates resolution has not included the correct wording on due dates and penalty payments.
The flaw was discovered when an analyst from the Department of Internal Affairs spotted it while going through the council's rating regulations.
Council chief executive Jane Parfitt met with the Department of Internal Affairs last Friday to figure out how to resolve the problem.
Mrs Parfitt says any mistakes dating back to 2004 will be corrected.
She says a more detailed report will be given to councillors at a meeting next Thursday 29 August.
The Auditor General's office is checking to confirm how much money is involved.