If you're planning on gifting millions of dollars to organizations and family members while you're alive, do it now.

The Tax Cuts and Jobs Act raised the gift and estate tax exemption — also known as the unified credit — to $11.18 million per person in 2018, more than doubling the limit under the old tax law.

This means that any one person could transfer more than $11 million, either in the form of gifts while alive or in bequests after death — and do so without having that amount be subject to the 40 percent gift and estate tax.

Wealthy families should know that while they have the blessing of the IRS to make large gifts for now, the exemption is set to fall back to about $5 million per person at the end of 2025.

Accountants are questioning whether that means that gifts in excess of $5 million might be clawed back into the donor's estate and hit with the gift and estate tax if you die after 2025.

"Many people are concerned about having a claw-back," said Andrew M. Katzenstein, partner in the private client services department at Proskauer Rose in Los Angeles. He spoke at the American Institute of CPA's ENGAGE conference in Las Vegas on Monday.

"They're thinking about what kind of planning they should do if they make big gifts and die when the exemption is down," he said. "Will Congress say that you made an $11 million gift, but now it's $5 million, so that $6 million gets clawed back?"

For now, the answer is "nobody knows," said Katzenstein.