Researchers at Victoria's Deakin University are investigating whether the schemes are leaving customers worse off than when they pay with other methods like credit cards.

Afterpay is among the most well-known buy now, pay later services in Australia, however more are joining the market, including Commonwealth Bank's StepPay.

While many people use the services responsibly, they can be a recipe for financial difficulty for some, Deakin School of Psychology researcher Dr Hannah Bereznicki said.

"When it comes to on-premises consumption, people are more likely to make their purchasing decisions while intoxicated, which could lead to poor decision-making, such as over-spending and over-consumption."

Buy now, pay later services are interest-free when users meet their payback deadlines, but late or missed payments can attract hefty fees and penalties.

Some schemes that don't have fees still encourage people to overcommit financially, Dr Bereznicki said.

More than 60 per cent of Australian buy now, pay later users report spending more money than they normally would through the schemes, according to the Australian Securities and Investments Commission.

Of people who use the services, 16 per cent report putting off other bill payments, becoming overdrawn, or seeking to borrow money because of overspending.

The commission also found young adults, who are more likely to be financially vulnerable, are the biggest users of the schemes and those aged 18 to 34 are most likely to be hit with late payment fees.

"(Buy now, pay later) is unregulated credit, meaning that financially vulnerable people may be more likely to access a loan than use credit cards, and they will receive less protection if they do get into financial difficulty," Dr Bereznicki said.

"We also know that some people resort to paying off their repayments with high-interest credit which drives them further into debt."

Injuries, assault, and emergency department presentations are linked to alcohol consumption, study investigator Professor Peter Miller said.

"If alcohol is perceived to be cheaper due to payment instalments, people may drink more than they intended and could be at greater risk of experiencing these harms," he said.

The Deakin University researchers are looking for Australians aged 18 and over to join in their online study "Booze now, pay later", about using different methods to buy alcohol. They are recruiting participants through the university website.

Most pubs and clubs offering the payment methods are located in Melbourne, Sydney, Brisbane, and Perth, while pay later alcohol home delivery is offered across the country.

Australian Associated Press