Palmer apologised for the "confusion" the mishap had caused ratepayers.
"Originally a penalty would have been applied from September 21 this year, but in recognition of the impacts of Covid-19 and the drought, we reverted back to February 1as per previous years," he said.
"This policy change was reflected in the rates newsletter we sent ratepayers, however, we missed the reminder was still on the front of the invoice, and the wrong penalty date was included on the back page of the emailed invoices."
Palmer added: "We are sorry that this has added stress at a difficult time."
A 10 per cent penalty still applies after February 1.
The council announced they'll not be increasing rates revenue this year, citing the financial impact that Covid-19 and the drought on the community.
Palmer also clarified the rating year hasn't changed and the invoice is for the full rating year from July 1, 2020, to June 30, 2021.
"We encourage people who are experiencing financial difficulty to contact our rates team and organise a payment plan. If you are on a payment plan, you won't incur any late payment fees," he added.