The start of online sports gambling came a little over a month after the state began allowing in-person sports betting at the state’s three casinos – Encore Boston Harbor in Boston, Plainridge Park Casino in Plainville, and MGM Springfield in Springfield.

Lawmakers estimate that sports betting could generate about $60 million in annual tax revenue and $70 million to $80 million in initial licensing fees, which must be renewed every five years. The law includes a 15% tax on in-person wagering and 20% tax on mobile wagering.

People must be 21 or older to bet.

At the headquarters of Boston-based sports betting company DraftKings, workers have been gearing up for the kickoff of online sports wagering in the state.

The company was already taking bets in more than 20 states where sports wagering is legal, but the prospect of serving fans of the Boston Red Sox, Boston Celtics, New England Patriots and the surging Boston Bruins is an added thrill, according to company president and co-founder Matt Kalish.

The company is also thrilled that the launch came just before the start of the NCAA basketball tournaments, he said.
“The most common way people jump into the product is usually for some big sports event. It might be the Super Bowl or something upcoming like March Madness,” he said. “So we’re launching in Massachusetts just in time for what should be an amazing tournament.”

The U.S. Supreme Court in 2018 ruled that banning sports betting was unconstitutional.

Former Republican Gov. Charlie Baker signed the bill legalizing sports betting. Baker, who is not president of the NCAA, argued that residents were traveling to Rhode Island, New Hampshire, New York and Connecticut to wager.

Representatives of professional athletes are asking officials in Massachusetts to toughen regulations to protect players and their families from being threatened by those wagering on games.