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Donald Trump’s charitable foundation — which has been sustained for years by donors outside the Trump family — has never obtained the certification that New York requires before charities can solicit money from the public, according to the state attorney general’s office.

Under the laws in New York, where the Donald J. Trump Foundation is based, any charity that solicits more than $25,000 a year from the public must obtain a special kind of registration beforehand. Charities as large as Trump’s must also submit to an annual audit that asks — among other things — whether the charity spent any money for the personal benefit of its officers.

If New York Attorney General Eric Schneiderman finds that Trump’s foundation raised money in violation of the law, he could order the charity to stop raising money immediately. With a court’s permission, Schneiderman also could force Trump to return money that his foundation already has raised.

The Trump campaign did not respond to a request for comment Thursday.

Schneiderman’s office declined to comment on whether it was investigating the lack of registration for the Trump Foundation. Schneiderman previously had launched an investigation of the foundation in the wake of reports by The Washington Post that Trump used his charity’s money to make a political gift, to buy paintings of himself and to settle legal disputes involving his for-profit businesses.

Tax filings show that in each of the past 10 years for which there are records, the Trump Foundation raised more than $25,000 from outsiders. Tax records alone do not reveal whether the donations amounted to solicitations under New York law, but in several cases there is strong evidence that they did.

For instance, the foundation has received more than $2.3 million from companies that owed money to Trump or one of his businesses — but that were instructed to pay the foundation instead, according to people familiar with those transactions.

In the most obvious example of a public solicitation, the Trump Foundation set up a website early this year to collect small-dollar donations that it promised to pass along to veterans. In all, the website said, the Trump Foundation took in $1.67 million through that site.

But, as of this week, the Trump Foundation had not obtained the state registration required to ask for donations, according to a spokesman for Schneiderman.

Experts on charity law said they were surprised that Trump’s foundation — given its connections to a wealthy man and his corporation — did not register to solicit funds.

“He’s a billionaire who acts like a thousandaire,” said James J. Fishman, a professor at Pace University’s law school in White Plains, N.Y. He said Trump’s foundation seemed to have made errors, including the lack of registration, that were more common among very small family foundations.