For the former heavyweight champion Mike Tyson, a cash machine to himself and to others, record earnings in the boxing ring became a license to spend -- on jewelry, mansions, cars, limousines, cellphones, parties, clothing, motorcycles and Siberian tigers. Despite making about $400 million over the past 20 years, Tyson managed to squander his fortune.

One of his most recent extravagances came on Dec. 22, when Tyson walked into a Las Vegas jewelry store and picked up a $173,706 gold chain lined with 80 carats in diamonds. But he never paid for the fabulous jewelry, which is among the $23 million in debts specified in the Chapter 11 petitions he filed Friday with the United States Bankruptcy Court in Manhattan.

Tyson's free-spending past made him creditworthy at Jewelers Inc., which he departed without paying a cent for the diamonds. ''Knowing him for so long, I gave him the merchandise and knew he'd pay later,'' Mordechai Yerushalmi, the store's owner, said by telephone yesterday. ''He had open credit with me.'' He added: ''He's been through his ups and downs. He will make good on it.''

That may not be easy. At 37, Tyson's boxing skills are diminishing, and so is his earning power; he could once command $30 million for a night's work. His future earnings and the future proceeds from the sale of a Connecticut mansion will go to pay a $9 million divorce settlement to his ex-wife, Monica Turner. She also has a lien on Tyson's Las Vegas estate, which is beside Wayne Newton's.