Congress' leading tax writers met yesterday to discuss easing economic uncertainty caused by pending tax legislation, but agreed only to study the possible effects of postponing the effective dates of the House-passed bill.

The market for tax-exempt bonds, including municipal bonds, is in disarray and businesses have cut their planned spending because of confusion over the sweeping tax-revisons bill, which is written to take effect on Jan. 1 of this year. Because the Senate has not yet acted, it is not clear when the ultimate legislation would be effective, if it becomes law.

House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) and ranking Republican John Duncan (Tenn.) met yesterday with Senate Finance Committee Chairman Bob Packwood (R-Ore.). The Senate Finance Committee is tentatively scheduled to begin writing its own tax legislation in early March. Packwood, however, recently has been saying privately that committee drafting sessions may not begin until mid-March or later.

Meanwhile, Sen. William V. Roth (R-Del.) yesterday announced a new tax-overhaul package that includes lower tax rates for businesses and individuals and a business transfer tax that would levy an 8 percent tax on the difference between business' costs (with some exceptions) and their gross receipts. A credit would effectively focus much of the tax on foreign companies importing to the United States.