SHOPS and restaurants could face fines up to $1.1 million if waiters or sales staff wrongly blame the carbon tax for price rises or exaggerate the impact.
And households are being warned to watch out for telephone scammers offering to deposit carbon tax compensation into their bank accounts.
The prices watchdog, the ACCC, will today launch its countdown to the July 1 carbon tax with a special focus on helping small businesses understand their obligations and consumers to be vigilant for false claims.
It is releasing internet videos to help business, a 16-page guide and has set up a dedicated website www.accc.gov.au/carbon.
ACCC deputy chairman Dr Michael Schaper told the Herald Sun companies were entitled to increase their prices and did not have to justify or explain why.
"It is business as usual,'' Dr Schaper said.
But if they blamed the carbon tax they must be able to prove it and not use it as a cover for other price increases related to wages, rent or stock.
"If a business claims that a price is linked to the carbon price, that claim must be truthful and have a reasonable basis,'' he said.
Dr Schaper said the warning applied to comments made by staff over the phone, on the shop floor or in meetings.
It also covers advertising, product labels, websites, invoices, contracts and contract negotiations.
The ACCC has the power to force a business to substantiate that a price rise has been caused by the carbon tax.
The guide explains what businesses can and cannot do, and provides a checklist to follow.
Dr Schaper said businesses must be sure price rises were "based on your own costs''.