The Internal Revenue Service yesterday released the principal income tax forms that businesses will use under the new tax code that went into effect this year.

The forms still could be changed before the final versions are printed this fall and sent to business taxpayers.

Some, such as the basic Form 1120 tax return filed by corporations, include relatively few changes from the forms in effect for tax year 1986.

Others, such as the return filed by taxpayers who receive income from partnerships, include extensive changes reflecting the law's crackdown on tax shelters and new rules on taxation of inventories.

Also released yesterday was the form that wealthy individuals will fill out to see whether they must pay the new minimum tax, which is intended to assure that people with sizable incomes pay at least 21 percent of their income in taxes.

The minimum tax, which essentially limits the deductions taxpayers can take to reduce their taxable income, was strengthened significantly in last year's law, and more than half the lines on the complex form are new.

Anyone who wants copies of the preliminary forms can write IRS, CADC, 2402 East Empire, Bloomington, Ill. 61799.

Interested parties also can submit comments on the changes they would like to see in the new forms by writing Tax Forms Committee, Attn: Early Release, Internal Revenue Service, Room 5577, 111 Constitution Ave., Washington, D.C. 2022