Michael R. Bloomberg, a multibillionaire who has flooded the country with more than $200 million in television and digital ads in his first two months as a presidential candidate, has requested and received an extension that will allow him to keep details of his vast personal fortune hidden until after millions of Americans vote in the 2020 primary.

The extended deadline for Mr. Bloomberg to file his financial disclosure form is now March 20 — more than two weeks after Super Tuesday, a day when roughly 40 percent of the delegates in the race will be up for grabs and after the Democratic primary could already be effectively decided.

“When people run for federal office, they’re supposed to provide this information,” said Meredith McGehee, the executive director of Issue One, a campaign watchdog group. “It’s not about whether I think so. The law thinks so.”

But because Mr. Bloomberg entered the race so late — in November, months after his leading rivals — he is still eligible for disclosure extensions deep into the primary calendar. And if Mr. Bloomberg were to drop out of the race before March 20 — say, after a disappointing showing on Super Tuesday — he could exit without making any financial disclosures of his fortune, which is worth an estimated $50 billion.