Residents of South Northamptonshire will be receiving replacement Council Tax bills in the next week or so after the originals were issued with incorrect figures.
Last week around 36,000 bills landed on doormats around the district, but due to human error the figures were calculated incorrectly.
Leader of South Northamptonshire Council, Cllr Ian McCord, said: “I should like to personally apologise.
"We now know what went wrong and we have a solution but this does not reflect the high-standards that residents deserve, so I want to say sorry.
"The error is relatively small; the incorrect bills show people owe an average £20 less than they should for a Band D home, or an average of £40 too little for a Band H property.
"I wholeheartedly apologise to residents and want to assure them the replacement bills will be thoroughly checked and no one will pay a penny more or less than they should."
Direct Debit payments due on Monday 1 April as stated in the original bills will not go ahead, and the correct sum will instead be taken on 15 April, and thereafter on the first of each month for those paying in instalments.
The new bills will be printed on light yellow paper, so as to help residents quickly spot the newly reissued, corrected bills, and avoid confusion.