The rules, which took effect Sept. 30, let wealthy donors, working through charities such as private foundations, put shares of publicly traded U.S. companies directly into Trump Accounts, the tax-advantaged investment accounts for children that launched July 4. As of Oct. 1, the Treasury had opened an account for nearly every eligible child under 18, or about 60 million kids. 

Previously, money in Trump Accounts went into low-cost index funds, which spread an investment across hundreds or thousands of companies, theoretically lowering the risk of losing everything if one company tanks. But the new rules make an exception for donated stock, opening the door for the ultrawealthy, whose fortunes are often tied up in shares of the companies they’ve built. 

“For a founder sitting on billions of dollars of appreciated stock, this could be an extraordinarily attractive way to give,” Kevin Gentry, founder and CEO of nonprofit fundraising consultancy TenX Strategies, told Fortune.

Shotwell and her husband, Robert, said in July they would “gift a share of our SpaceX stock to a Trump Account for each of more than two million children across our great nation,” she wrote on X. The gift targets kids ages 11 to 17 in lower-income areas, with extra emphasis on those near the couple’s central Texas home. At the time, President Donald Trump valued the gift at $325 million, and as of Thursday (assuming the current share price) it would be worth about $330 million. Shotwell announced her pledge before Treasury finalized the rules, which now require stock gifts to come through a charity and win Treasury’s approval.

Shotwell has been the only donor to announce a major stock gift, the Wall Street Journal  reported, but Treasury notes show others have expressed interest in similar donations. That raised the question of whether the world’s first trillionaire would participate. While Elon Musk has criticized other philanthropists like MacKenzie Scott and lamented the difficulties in giving effectively, he’s also hinted at giving his wealth away.

SpaceX did not respond to Fortune’s request for comment. 

Where the tax savings come in

For the ultrawealthy who decide to practice philanthropy through Trump Accounts, the tax break looks a little different.

“There is no tax deduction for giving either stock or money to Trump Accounts,” Scott Hanson, cofounder of wealth management firm Allworth Financial, told Fortune. Savings come later on. Only governments, tribal governments, and charities can make these stock gifts, so billionaires have to move their shares into a charity first. 

“The tax play is the stock they transfer to a foundation prior to gifting to a kid’s Trump account,” Hanson said. 

Donors who give a private foundation publicly traded stock they’ve owned for more than a year can generally deduct its full market value, up to 20% of their adjusted gross income each year, with any excess carried forward for up to five years, according to the IRS. And because giving stock away isn’t a sale, “there is no taxable gain to tax,” Sherman Standberry, a CPA and CEO at tax consulting firm My CPA Coach, told Fortune.

Gentry offered an example of why that matters. A founder who, say, paid $1 million for stock now worth $100 million would generally realize $99 million in gains by selling it, and likely owe significant taxes on that. 

He questioned: “Why sell an appreciated asset, pay the tax, and give what’s left when the tax code may allow you to give the asset itself?” While none of those perks are new, what is is where the stock can end up. 

What donors and kids get

Another potential upside for donors is a whole new class of shareholders, Gentry said. Treasury acknowledged that appeal in its rules, writing that donors hope a five-year holding period “may lead recipients and their families to feel that they have a stake in the fate of the corporation.”

But that also ties some kids’ savings to a single company’s fortunes. The same rules acknowledge that kids “will bear some additional risk in the form of increased portfolio concentration” when donations come as stock rather than cash. Families, meanwhile, can’t choose the stock or, for now, refuse it. Shares generally must be held for five years, or until the end of the year a child turns 17.

Gentry said a foundation handing out its founder’s stock raises legal questions, including over self-dealing, and its board should be ready to explain the decision.

“The important question is whether the philanthropic purpose is driving the transaction,” he said.

The Treasury declined Fortune‘s request for comment.