The House Ways and Means Committee decided yesterday to resume work tomorrow on President Carter's long-stalled tax-reduction plan, with an eye toward replacing it with a conservative substitute that would slash taxes on capital gains.

Tomorrow's session was scheduled by Chairman Al Ullman (D-Ore.) after a day-long caucus yesterday in which senior committee members reached informal agreement on a compromise by Rep. James R. Jones (D-Okla.).

The committee is expected to approve quickly some version of the Jones measure, which would trim the size of the overall tax cut to $15 billion, rather than the $19.4 billion carter now is requesting, and would roll back part of the 1969 tax boost on capital gains.

Jones' substitute was designed to break a deadlock in the committee over a proposal by Rep. William A. Steiger (R-Wis.) that would have completely rolled back the 1969 increases. Liberals had threatened to scuttle the whole bill if Steiger's provision passed.

Committee sources estimated the Jones proposal would draw more than enough votes to win formal approval. The Carter administration still opposes the measure on capital gains, but has not raised strong objections to the rest of the proposal.

Meanwhile, Chairman Robert N. Giaimo (D-Conn.) of the House Budget Committee raised the possibility that his panel may try to cut back even further the $19.4 billion limit for the tax-reduction bill allowed in the new congressional budget resolution.

While declining to suggest what the new limit should be, he cautioned in an interview that "we don't want to build in a tax cut that is too big." He hinted he may try to slash the tax bill further when Congress reconsiderse the budget resolution in September.

There were indications yesterday Carter might agree to the further cutback. Although the president is said to be reluctant to suggest such a move, some top advisers have been urging the step privately and say he might not object if Congress trimmed the package.

The developments came as, separately, a Ways and Means subcommittee approved legislation that would repeal a provision in the 1976 Tax Reform Act toughening the tax treatment of Americans living abroad, and would give them additional tax breaks.

The decision, which must be reviewed by the full committee, would cost the Treasury only $85 million less than it would take to exempt overseas Americans from paying U.S. income taxes. The 1976 law had sought to crack down on alleged abuses.

The compromise on capital-gains taxes proposed by Jones would reduce the maximum effective tax rate on capital gains from 49.1 per cent to 35 percent. Steiger's proposal would have slashed it to 25 percent. Capital gains are profits from the sale of stocks or other assets.

The Jones and Steiger amendments are directly contrary to what Carter had hoped to accomplish on the capital gains question. As a candidate in 1976, Carter pledged to end special tax treatment of capital gains and instead tax them as ordinary income.

The substitute proposed by Jones effectively would scrap the major taxcut and "tax-reform" provisions that Carter recommended last January and replace them with a more traditional package comprising $10 billion in cuts for individuals and $5 billion for business.

The major elements include:

Scuttling Carter's tax-cut plan for individuals and instead trimming personal taxes by raising the $750 personal exemption to $1,000 for taxpayers and their families, and cutting individual tax rates. The $35-a-person tax credit would be repealed.

Reducing business taxes by cutting the 48 percent corporate tax rate to 46 percent in 1979, and raising from $50,000 to $75,000 the amount of company earnings taxed at lower rates. Carter's proposal for a permanent 10 percent investment tax credit would be retained.

Scrapping all of Carter's proposed tax "reforms" except for repeal of the deductions for state and local gasoline, sales and personal property taxes. The president's proposal to end deductions for the three-martini lunch would be replaced by extra appropriations to help the Internal Revenue Service audit expense accounts.

Committee leaders are scheduled to meet this morning to iron out details on possible amendments the panel will recommend for separate floor votes when the tax bill goes to the House. Among the candidates are the original Steiger amendment and a move to retain the deduction for state and local sales taxes.

The overseas tax bill approved by the subcommittee yesterday would restore the pre-1976 provisions allowing Americans abroad to earn $20,000 a year tax-free in all countries except Canada and those of Western Europe. In addition, there would be special deductions for housing and other expenses.