President Carter's taxwriters have pared even further their already scaled-back proposals for his tax revision program - reducing it simply to the expected tax cuts for individuals and business and a handful of modest changes in the present tax code.

In planning sessions this past weekend, members of the administration's key tax policy group reportedly hammered out recommendations that would scrap virtually all of the original, more comprehensive program, including a compromise package being considered last week.

Treasury Secretary W. Michael Blumenthal told a news conference in New York yesterday the recommendations would go to Carter for a final decision next weeks, after tax planners finish squaring the proposals with the impact of the pending energy tax bill.

Although Bluementhal did not spell out details of the coming package, tax sources familiar with the program said the Treasury's recommendations were even more muted than had been expected earlier. One official said there would "hardly be any reform at all."

While officials would not comment publicly, insiders said the tax policy group already has ruled out the center-piece of the earlier Carter proposals - a move to end the special tax treatment of capital gains, the profits from sales of stocks or other assets.

The tax writers reportedly also have scrapped a key Carter proposal to reduce the so-called "double taxation" of corporate profits and dividends, which some had assumed would remain even in the pared-back version. The end of double taxation is heavily favored by key members of Congress.

Still uncertain at this point is whether the administration will follow through on Carter's campaign promise to end two foreign tax breaks - the present tax subsidy for experters and the provision allowing corporations to defer payment of taxes on foreign-source income.

However, officials hinted yesterday that many of the proposals being considered as late as last week no longer were part of the official package. The Treasury had been considering a series of "option papers" listing a dozen or so of these provisions.

It was no immediately clear whether Carter would accept the group's proposals. Although the White House has felt hamstrung somewhat by political opposition to tax-revision, Carter is said to be strongly for "meaningful reform."

However, the Treasury proposals reportedly have been endorsed by Stuart E. Eizenstat, the President's chief domestic adviser, who is coordinating the tax revision effort. As such, insiders say, it's unlikely the Treasury recommendations will be overturned.

The cutback came as a disappointment to some liberal tax experts, who had hoped the administration still would salvage a "respectable" tax revision package this year. Carter earlier had been considering a major proposal for overhauling the tax system, but backed from it last month.

The President has hinted he may seek to revive some of these earlier "reform" proposals in a second tax bill early in 1979, but plans for such a move reportedly still are sketchy. Some analysts see little chance Congress will make major changes in anycase.