And that management fee isn’t deductible anymore. “So you’re paying tax on 10 percent, although you’re only really getting 8 percent.” Add to that any state and city taxes, which can boost your effective tax rate to almost 70 percent.

“So what you are left with is that original 12 percent return, which sounded so great, is closer to 3 percent,” Stein says.

The landscape for trusts and other investment vehicles has also dramatically changed under the Trump administration’s tax reform. The law wiped out many tax exemptions and other tax reduction strategies for family offices, according to Withersworldwide professionals.

“We think taxes have been cut, and yet most of our clients are saying, ‘My taxes have gone up. What’s going on?’” Stein adds. He says the tax package also eliminated some traditional deductions and exemptions used by high-net-worth clients.

“There are strategies that we wouldn’t have used before, because they were inefficient prior to this year, that are suddenly in play,” Stein says. Before now, one might have avoided using a corporation, for instance, because the tax rate was high. Today, because the corporate rate is now down to 21 percent, Withersworldwide’s advice might change.

For those reasons, Stein and other firm officials say there are new areas of opportunity that were once shunned as inappropriate.

So with the lower rate, “today we can think about using corporations even though it means two layers of taxes, while historically we might have said that it doesn’t make any sense to have two layers of taxes,” Stein adds.

And there’s another problem, the firm says: The tax reform affects the way foreign grantor trusts hold U.S. situs assets, which define where a property is held for legal purposes. Exemption rules were changed under the tax law, which can affect the way foreign grantor trusts (FGTs) hold situs assets.

“In view of this change, trustees of FGTs should revisit their strategies for protecting U.S. situs investments from U.S. estate tax on the eventual passing of the trust’s non-U.S. grantor,” says a Withersworldwide consulting paper on the subject, “Foreign Grantor Trusts, U.S. Situs Assets And 'Check The Box' Planning Under The U.S. Tax Reform Act.”

For instance, “under the pretax reform law, trustees of FGTs generally could use non-U.S. holding companies to provide estate tax protection for U.S. situs assets and then, following the grantor’s death, effectively eliminate those holding companies.”