Home buyers, sellers and real estate investors who are worried about tax reform on Capitol Hill can begin filling in their score cards with some early wins and losses. The tax-writing Ways and Means Committee reached its first major real estate decisions in the final week of October and gave important hints on where the entire reform bill is headed this year.

For starters, the committee rejected President Reagan's proposal to kill low-interest-rate mortgages for first-time home purchasers financed through local and state tax-exempt-bond programs.

The politically popular cut-rate bonds financed nearly 300,000 new and resale houses for first-time buyers in 1984. They were targeted for termination next Jan. 1 under the White House's tax-reform package.

The Ways and Means Committee voted instead to rein in the total mortgage volume of tax-exempt home mortgage bonds and to tighten eligibility rules for would-be beneficiaries.

The committee's rewriting of the rules could reduce the number of homes financed nationwide in a typical year by as much as one-third, according to bond experts. But the committee left intact the core concept of tax-exempt financing.

The committee also took steps last week to preserve tax-code preferences for investors in low-income housing, and agreed to retain tax-exempt industrial-development-bond-financing authority for a wide variety of local real estate projects, including rental apartments.

President Reagan's tax reform bill would have killed them all next New Year's Day. The House Ways and Means Committee rejected that death sentence, in effect, but did impose new state-by-state volume restrictions on such projects.

Still to come on the committee's agenda in the next two weeks are some of the most fundamental issues involving American real estate tax policy. These include such political hot potatoes as depreciation write-offs for residential rental and commercial-income properties, the deductibility of local and state property taxes, tax treatment of second-home vacation retreats, capital gains and minimum-tax provisions, and tax credits for historic and other rehabilitations, plus a raft of proposed code changes that would cripple the burgeoning, multibillion-dollar real estate syndication industry.

So where is the tax bill really going in the remaining weeks of the year? What's likely to be in it, and what -- if anything -- will change for real estate taxpayers when Jan. 1 rolls around? Based on discussions with House and Senate staff members, plus the Ways and Means Committee's own actions late in October, it's possible to come up with at least two basic ground rules.

First, the operative political formula for tax-bill writing in the House at the moment is this: Nobody dies, but everybody gets hurt at least a little.

Translated into real estate legislation, that means: If you're worried about the continued existence of historic rehabilitation credits, second-home deductions or tax-oriented real estate partnerships, don't bite your nails to the quick. The tax rules will be modified to lessen federal revenue losses, but your favorite program is likely to survive.

The corollary for ardent tax reformers who hoped for true tax-code simplification is this: Forget it. The intense political back-scratching necessary to coax a bill out of the House requires greater complexity to the code, not less; more loopholes, not fewer. President Reagan's dream of a streamlined federal tax code died Halloween week.

Second, don't plan on -- or worry about -- Senate adoption of a tax bill in 1985. The leader of the Senate's tax-writing committee, Bob Packwood (R-Ore.), has ruled that out.

He said "it would be a colossal mistake" for the Senate to rush through a vast tax reform bill in December, even if the House produced one for consideration the week after Thanksgiving. Look to either next Easter or early summer for legislation, not before, Packwood advised.

But what about the Jan. 1 effective date for many of the provisions in the tax proposals?

They could pose problems, but a bipartisan coalition in the Senate is forming behind a resolution that would reset the effective dates to next July 1, at the earliest. Co-sponsored by Sens. Alphonse D'Amato (R-N.Y), Christopher Dodd (D-Conn.) and Paula Hawkins (R-Fla.), the bill would be the most significant -- or the only -- real estate tax legislation Congress passes this December.