Groupon’s practice of selling group-discount coupons with expiration dates is being reviewed by Connecticut Attorney General George Jepsen for possible state law violations.

“It appears that what Groupon Inc. sells or offers may fall within the definition of a gift certificate under Connecticut law,” Jepsen said yesterday. “Connecticut law prohibits gift certificates from being sold or issued subject to an expiration date.”

Groupon, which delivers daily discounts on hotels, restaurants and other goods and services to 83.1 million subscribers, may generate $3.9 billion in US sales in 2015, up from $873 million in 2010, according to the research firm BIA/Kelsey.