Australians lost more to scams in 2016 but the $300 million reported to authorities is believed to be just the tip of the iceberg.
Scammers are increasingly using social media to find their victims and becoming more threatening, costing Australians at least $300 million last year.
One Australian lost $1.6 million to a fake online investment in 2016, as investment scams and dating and romance scams again led to the highest financial losses reported to authorities.
Australian Competition and Consumer Commission deputy chair Delia Rickard says it is not difficult to see why Australians are losing money to these scams, which are often very sophisticated and targeted.
"They put a lot of time and effort into grooming people in both the romance scams and the investment scams because they are so lucrative," Ms Rickard said.
"They're also - and I think social media makes this easier for them - very good at targeting those that they know are most likely to not just fall for the scam but to have some money behind them."
Australians aged 55 to 64 are being targeted by dating and romance scams, while those aged 45-54 are most affected by investment scams.
"They target age groups where people do have some money so the scam is going to be even more profitable," Ms Rickard said.
The $299.8 million lost to scams by Australians in 2016 - up $70 million on the previous year - is believed to be only the tip of the iceberg as many victims do not go to the authorities.
An Australian Bureau of Statistics survey last year estimated the total amount lost to personal fraud to be closer to $3 billion.
Ms Rickard said there had been a sharp increase in scams taking place through social media sites, the most common being dating and romance scams and fake online stores.
Scammers have also used more threatening tactics and made more covert payment requests in an attempt to outwit their victims, the ACCC said in its annual Targeting Scams report, released on Monday.
Ms Rickard said scammers impersonating a variety of government agencies were targeting particularly vulnerable groups such as people in Australia on a visa or Centrelink recipients to scare them into parting with their money.
The bulk of the threat-based scams involved tax scams.
Losses from investment scams reported to the ACCC and the Australian Cybercrime Online Reporting Network increased to $59 million in 2016.
Losses through dating and romance scams fell to $42 million but the scammers are increasingly using social media, particularly Facebook, to find their victims instead of online dating sites.
"Dating and romance scams have now evolved on social media platforms, and often involve blackmail through sextortion," Ms Rickard said, referring to the use of compromising images of the victim to extort money.