Jere Doyle, wealth strategist at Bank of New York Mellon, said the wealthy should not get their hopes up for an end to the estate tax. He pointed out that an estate did not have to submit its first tax bill until nine months after a person’s death. The Senate could wait, then, until the summer to decide on the estate tax and make it retroactive to the beginning of the year. This would wreak havoc on estate planning. Even if the Senate acted early in the coming year, it could still lead to a flurry of legal challenges on the constitutionality of reinstating a tax that had disappeared.

But there is a broader issue for moderately wealthy people. When a person dies now, the value of his or her assets gets a “step-up in basis,” which means for tax purposes the assets are valued on the day of death. Without an estate tax, this provision disappears, and the appreciated value is subject to capital gains tax.

The Internal Revenue Service will grant a $1.3 million “artificial basis” on assets of a single person and $3 million for couples if the estate tax disappears. But on the rest of the assets, the heirs will have to determine what the original cost was and pay the capital gains on the appreciated amount. For long-held stock that has split many times, this could be extremely difficult.

“If there is no estate tax in 2010, we have an income tax problem for a larger group of the population,” Mr. Kesten said. He estimated that the number of people affected would go from 6,000 to 60,000.

Image Jere Doyle, wealth strategist at Bank of New York Mellon, said the wealthy should not get their hopes up for an end to the estate tax. Credit... Jodi Hilton for The New York Times

Still, most advisers and accountants expect that an estate tax will be reinstated, and this has pushed the wealthiest to find new ways to reduce its impact. “If we’re resigned to an estate tax existing, it’s not a call on where rates will go but an acknowledgment we won’t have a repeal,” said Janine Racanelli, managing director and head of the Advice Lab at J. P. Morgan Private Bank.

One way is through giving money to heirs above the $1 million lifetime exemption level and paying the 45 percent gift tax now. This may seem odd at first, since the estate tax is currently the same rate. But the benefit comes from how the taxes are applied: the gift tax is added like sales tax, while the estate tax is deducted like income tax. Mr. Kesten noted that a person with a $30 million estate could give roughly $20 million to his heirs during his lifetime and pay $10 million in gift taxes, or he could leave the $30 million to them and they would receive $15 million, after estate taxes.