Everyone knows that death and taxes are inevitable. The House Ways and Means Committee wants to demonstrate that they also are inseparable.

In their search for ways to increase federal revenue, congressional tax writers are focusing increasingly on the estate and gift tax, which has been unchanged since major reductions were enacted in 1981. With opposition rising to such other options as higher excise taxes, the estate tax is becoming a more tempting target as legislators attempt to raise taxes by as much as $19.5 billion in 1988 alone.

Legislators are looking at three ways of raising revenue through the estate and gift tax: postponing further scheduled reductions in the tax rate, reducing the amount of estate income not subject to tax and limiting an estate-tax break related to capital gains taxation that is widely considered one of the biggest loopholes in the federal tax code.

In addition, the tax bill that emerges is almost sure to close a loophole opened in last year's tax law relating to estate taxes and employe stock-ownership plans.

Increases in the estate and gift tax alone could not raise enough money, but would hit the wealthy harder than would most of the other items under consideration -- an important factor if the final tax bill is to treat all income groups fairly.

"I think among committee members we think it is a good area to look at, far preferable to looking at income taxes," said Rep. Fortney H. (Pete) Stark (D-Calif.), who is interested in a tax, possibly of 1 percent, on the value of all estates when they are transferred.

In their meeting last week, four or five committee Democrats spoke favorably about raising revenue through the estate and gift tax.

"Some changes in estate-tax law could qualify both as money-raisers and as ways of making the tax code more fair," said Rep. Donald J. Pease (D-0hio).

The committee is a long way from agreeing on a final tax bill. Proposals from members are due today for items they would like to see considered in a tax package, and hearings do not begin until late June. Efforts to collect more revenue through the estate tax have been stymied in the past by strong lobbying by lawyers, bankers, farmers and small-business organizations.

But there are few sources of revenue available for deficit reduction this year, now that Congress has cut back tax breaks in the 1986 tax-revision law. Committee chairman Dan Rostenkowski (D-Ill.) has declared off limits the new tax rates for individuals, and higher excise taxes are raising regional and special-interest opposition.

"There's a lot of money there in the estate-tax area," said Robert S. McIntyre, director of Citizens for Tax Justice, a labor-funded research and advocacy group.

Revenue collection from the estate and gift tax -- actually two parallel taxes with the same rate structure -- has been declining since Congress cut the top tax rate from 70 percent to 50 percent and increased the tax-exempt amount from $175,000 to $600,000 in 1981. That year, estate and gift taxes brought in about $8 billion.

The liberalizations, which were phased in over five years, are expected to reduce the revenue figure to $6 billion in fiscal 1987 and to $4 billion by 1991. As a share of total federal revenue, the estate and gift tax has fallen from an average of about 1.5 percent during the 1960s and 1970s to 0.7 percent in 1987.

Although there are no recent figures, indications are that only the wealthiest Americans generate estate taxes when they die and pass on their assets. In 1983, the Joint Committee on Taxation found that only 2.3 percent of all deaths led to payment of any estate tax.

Ways and Means members said their panel is likely to consider freezing the top estate-tax rate at the current 55 percent rather than allowing it to fall to 50 percent next year as scheduled. That would only affect estates worth more than $3 million.

Another possibility is dropping the tax-exempt cutoff below $600,000. The committee also may consider limiting a tax benefit that, by Joint Tax Committee estimates, costs the Treasury more than $4 billion in revenue per year.

The benefit works this way: If a person buys an asset that then increases in value, and the investor dies, the heir inherits that asset on a market value "basis" for tax purposes. If a share of stock is bought at $10 and appreciates to $100, for example, the owner would owe capital gains tax on the $90 in appreciation if he or she sold the stock before dying. But if the person dies and passes on the stock the new owner can start over again, using $100 as the basis for calculating his gain when he or she sells the stock.

"It's a humongous loophole. I think it's scandalous," said Henry Aaron, a tax economist with the Brookings Institution. Limiting the benefit would be "perhaps the most progressive change you could make in taxation."

To farmers, small-business proprietors and other owners of assets, however, limiting the "basis" benefit is tantamount to repealing Motherhood. Either of the two possible ways to change it -- requiring that taxes be paid on the gain at death or transferring the older, lower basis to the heir -- would be strongly opposed by those groups.

"Our members would come out of the woodwork on that one," said Grace Ellen Rice, associate director of the American Farm Bureau Federation's Washington office. "We would just raise up, and any farm group will tell you the same."