Small business suppliers are being left empty-handed as new data reveals almost one in four big businesses takes more than 120 days to pay their invoices.
The Business Council has a 30-day payment goal but seven out of 10 big businesses are failing to meet the benchmark, according to the Payment Times Reporting Regulator.
"These figures are appalling," Australian Small Business and Family Enterprise Ombudsman Bruce Billson said.
"I say to the nation's big businesses who are making small business wait four months to get paid - you can't be serious."
The data was provided to the regulator by 7000 businesses, many with a turnover of more than $100 million.
The manufacturing industry was found to be the biggest culprit, with only 14 per cent of invoices paid within 30 days, closely followed by retail and construction.
The most reliable industries are public administration and safety, of which 54 per cent pay their invoices on time.
"For big business leaders urging support for small business 'doing it tough', a practical and achievable measure is to get serious about improving payment performance," Mr Billson said.
"Good businesses pay. That's a vital part of business relationships."
