Single-use plastic shopping bags have been banned in NSW ahead of further changes to eliminate other plastics later this year.
The ban came into effect on Wednesday after laws passed parliament in November.
Retailers who continue to provide the bags could face a fine of up to $275,000.
The state will expand the ban on single-use plastics in November to include straws, coffee stirrers, cutlery, plates, cotton buds, polystyrene cups and containers, and cosmetics containing plastic microbeads.
"I think all of us can see the impact plastic pollution is having on our environment, which is why we're making major changes in NSW this year," Environment Minister James Griffin said last week.
He said convenience does not make up for the permanence of plastic, and the single-use plastics make up about 60 per cent of all the state's litter.
"By stopping the supply of problematic plastic in the first place, we're helping prevent it from entering our environment as litter, or going into landfill," Mr Griffin said.
Exceptions will remain for people with disabilities or medical needs that require them using single-use plastics such as a straw.
The bag ban does not apply to bin liners or supermarket produce and deli bags.
The NSW government has worked with the National Retailers Association to provide education on the new laws and aid compliance, Small Business Minister Eleni Petinos said.
Opposition small business spokesman Steve Kamper said education programs were left too late and had inadequate reach.
"No one told these small businesses that plastic bags are banned ... now they're sitting on thousands of dollars' worth of bags they can't use," Mr Kamper said on Monday.
He said more notice and better government messaging would have prompted businesses to purchase paper or cardboard packaging months ago instead of ordering more plastic bags.
All other states and territories have already banned plastic bags, beginning with South Australia in 2009.
Major supermarkets Woolworths and Coles also stopped providing single-use plastic bags in 2018.
The thicker plastic bags sold in supermarkets are not banned by the new laws.
