The Internal Revenue Service yesterday introduced a simplified tax form for single taxpayers with no dependents and incomes of less than $50,000 a year.

It will, of course, be called 1040EZ.

The EZ form is one page long and has just 11 lines to fill out. Roscoe L. Egger Jr., IRS commissioner, estimated that it will be used by 11 million taxpayers in filing their 1982 returns next year. "It's as simple as we can make it," he declared.

In all, about 95 million returns will be filed next year.

In order to use the form, not only must a taxpayer be single with an income of less than $50,000 and no dependents, but the income must come almost entirely from wages, salaries and tips.

The one exception is up to $400 in interest income.

The form, the third basic form now available to individuals, allows a deduction of up to $25 for charitable contributions, and automatically provides for a $1,000 personal exemption.

The other two forms are the 1040A, which has two pages and 31 lines to fill in, and the 1040, which has two pages and 71 lines.

The 1040A can be used by anyone with income less than $50,000 from wages, salary, tips, interest, dividends and unemployment compensation, and it allows working couples to claim a deduction for the so-called marriage penalty, to make deductions for political contributions and to receive a refundable credit in the case of the working poor.

The 1040 form is for all taxpayers, including those with the most complex affairs. In many cases, it must be accompanied by additional forms. CAPTION: Picture, IRS Commissioner Egger introduces new form: "It's as simple as we can make it." UPI Illustration, This the 1040EZ for single people with no dependents and incomes under $50,000