WASHINGTON — The Treasury Department proposed a crackdown Tuesday on wealthy families attempting to avoid the estate tax.

The tax, dubbed the ‘‘death tax’’ by critics, is levied on estates worth more than $5.45 million per person or $10.86 million per couple. Anything above that level is supposed to be taxed at up to 40 percent.

But relatively few families subject to the tax pay that much; typically the hit is about 16.6 percent, according to some estimates.

‘‘Really, anyone who is not on death’s doorstop with a good [estate] planner can get the rate down to zero,’’ said Robert Lord, a tax attorney based in Arizona. ‘‘Sixteen percent is a high effective rate.’’

Now the Treasury Department has proposed new regulations it says will make it harder for families to avoid estate taxes.

‘‘It is common for wealthy taxpayers and their advisors to use certain aggressive tax planning tactics to artificially lower the taxable value of their transferred assets,’’ Mark Mazur, the department’s assistant secretary for tax policy, said in a blog post. ‘‘. . . Treasury’s action will significantly reduce the ability of these taxpayers and their estates to use such techniques solely for the purpose of lowering their estate and gift taxes.’’

For instance, some families put their assets in a limited liability company when looking for ways to lower their taxes, said tax lawyer Beth Kaufman, who previously served as associate tax legislative counsel for the Treasury Department. The family can then argue that the assets should be valued at a discount because selling a portion of the corporation would be difficult, she said. Applying that discount to the value of the assets obtained through an inheritance or given to a family member as a gift would lower the estate tax owed.

The tax community has been waiting for regulations on this issue since 1990, she said. ‘‘In this world, this is a big deal,’’ said Kaufman, president of the Washington, D.C., law firm Caplin & Drysdale.

The Treasury Department did not say how many families the change is expected to affect or how much additional tax revenue it expects to gain. But the estate tax is paid by few people, two out of every 1,000 estates, according to the Center for Budget and Policy Priorities. It is projected to bring in $249 billion between 2017 and 2026, according to the Congressional Budget Office, a small part of the federal budget.