Theater leaders will appear before the House Ways and Means Committee beginning tomorrow to oppose various Carter administration tax-reform proposals that would affect show-business finances.

The leaders are from both commercial non-profit theatrical organizations as well as other arts and trades groups. They argue that the administration appears to be giving to the arts with one hand and proposing to take away with the other.

The three areas of concern are:

The proposal to disallow certain entertainment expenses (such as theater tickets) as tax deductions. United against this are the nine theatrical unions that form the 4A affiliates - the Associated Actors and Artistes of America - and the Federation of Musicians, as well as other producing organizations.

The proposals to make a theatrical venture with more than 15 partners a commercial corporation instead of a limited partnership. Opponents believe this would dry up theatrical financing.

The proposal to tax the unemployment insurance of those earning more than $20,000 a year. The catch here, opponents point out, is that while some show-business professionals may earn that much one year they may have no certain income for the next and are therefore placed at a disadvantage.

Among those appearing will be Gerald Schoenfeld, chairman of The Shubert Organization, Inc., speaking for the National Association of Legitimate Theaters and the League of New York Theaters and Producers; Donald Grody for Actors' Equity Association; Jim Backas of the American Arts Alliance; James Nederlander for the Alliance of Arts and Artists; Sanford I. Wolff for AFTRA, the American Federation of Television and Radio Artists; Barbara Robinson of IATSE, the International Alliance of Theatrical Stage Employes; Vic Fuentealba of the American Federation of Musicians and Harvey Horowitz of the American Council for the Arts.

Speaking for the sports world will be baseball commissioner Bowie Kuhn and John A. Ziegler of the National Hockey League.

These groups claim that the tax proposals take a shotgun approach to essentially unique fields. "Blanket proposals," they declare, "will create hardships."