Ah, but remembering to bring that bag is another matter altogether. After all, New York is a place where people are almost programmed to do things impulsively, because it is so easy to just hop into a bodega or a deli or a 99-cent store to buy anything, anytime, no forethought required.

“You have to get used to using these,” said Lauren Robertson, 54, an occupational therapist who lives in Washington Heights, who was loading groceries in canvas bags into her car in the Fairway parking lot on 130th Street near the Hudson River on Thursday morning. “So many times I’d get into the store and realize I forgot my bags in the car.”

Bloomberg officials say the proposal remains a work in progress. But for now, the plan is to charge customers 6 cents a bag at the point of sale, with 1 cent going to the store owner as an incentive to comply, said Marc La Vorgna, a Bloomberg spokesman. The officials did not elaborate on the mechanics of how the money would be remitted to the city, or how the law would be enforced.

Image Bags at a Fairway store in Manhattan. Credit... Librado Romero/The New York Times

It sounds like a tax, but officials call it a fee. The distinction is important: A fee requires approval only from the City Council, while a tax requires approval from the State Legislature.

Unlike a number of ideas that seem to have been inspired by experiments in other countries (such as exploring wind power, based on windmills which Mr. Bloomberg saw off the coast of England, or temporarily closing off streets to cars, based on a program in Bogotá, Colombia, that the mayor had heard about), this one, city officials say, was hatched in the mayor’s Office of Long-Term Planning and Sustainability.

The idea is not totally foreign to the metropolitan area. The Ikea furniture chain, which opened its first New York City store in June, on the Brooklyn waterfront in Red Hook, began charging customers 5 cents for each plastic bag in 2007; since then, the store says, plastic bag use has been cut in half. Several large supermarket chains in the region, like Whole Foods Markets, offer refunds when customers bring reusable bags.