May 4, 1984

Sales of new cars by the nation's major manufacturers rose 36.6 percent in the last 10 days of April from a year earlier, the companies reported today. The increase was measured on a daily rate basis, with eight selling days in the period this year and nine last year. The seasonally adjusted annual selling rate, which has been bouncing up and down the last two months, rose to 8.3 million in the April 21-30 period, from 7.7 million in mid-April, to reach 8.1 million for the month, about what analysts had expected. Ann Knight, an auto analyst with Paine Webber Mitchell Hutchins, said: ''These are good strong sales. They are sustainable. When we are in a period resembling normal demand, as we are now, you're going to see some fluctuation from one 10-day period to the next. Between now and the end of the second quarter, anything between a 7.5-million and 8.5-million rate will not surprise me.''

Esmark Inc., the big Chicago company that bought Norton Simon Inc. last year for $1 billion, said yesterday that it had just received a takeover bid of its own for $2.3 billion in cash. It has yet to respond to the offer, but Esmark is widely known to be interested in making a deal, if an acceptable price can be struck. In a brief statement announcing the deal, Esmark said that it had been offered $55 a share for the company's 41.8 million shares outstanding, or $2.3 billion, by Kohlberg, Kravis, Roberts & Company, a New York investment house that specializes in management buyouts. Wall Street analysts, forecasting a bonanza for Esmark stockholders, said they expected other suitors to join in the bidding soon.

An obituary on April 15 of Carl K. Erpf, chairman of the Manhattan brokerage firm of Ladenburg, Thalmann & Company, misidentified Mr. Erpf's late father. He was Carl Erpf; Armand G. Erpf was the younger Mr. Erpf's uncle.

Because of a mechanical error, some copies of the Late Edition yesterday omitted page C11 and carried page C18 twice. Readers wishing copies of the missing page may write to Production Quality Control, The New York Times, 229 West 43d Street, New York, N.Y. 10036.

The Internal Revenue Service is proposing to ban a popular new type of fringe benefit plan that allows workers to use pretax wages to pay for medical and other personal expenses and take back in cash any unused portion. The regulations would require hundreds of thousands of workers who participated in one type of these so- called reimbursement or flexible spending accounts to pay back taxes and interest on benefits previously received. The reimbursement accounts are an outgrowth of the so-called cafeteria approach to employee benefits, whereby participants may choose from a menu offering day care, legal and medical and dental coverage. In all, employee benefit consultants estimate that as many as 200 major reimbursement plans covering between one million and three million employees will be affected by the regulations. Those who participated in the most liberal of these plans, known as zero-balance reimbursement accounts, or Zebras, will likely have to pay interest and taxes for any amounts reimbursed in the last three years, an I.R.S. spokesman said.