From 6,000 to 8,000 present and former members of the Senior Executive Service are scheduled to receive back payments of up to $5,900 in April under an agreement reached last week between attorneys for the government and SES members.

The payments are portions of pay raises Congress denied the executives between October 1979 and December 1981. Most of those due the payments live in the Washington area.

The SES back pay case has been dragging on for more than a year. The government originally opposed the pay awards, which were ultimately made by a U.S. District Court in Milwaukee, on the grounds that the court did not have jurisdiction in federal pay matters. But the Supreme Court declined to hear the government's appeal, and since then both sides have been trying to work out an agreement.

On Feb. 20, according to the Senior Executive Association, agreement was reached between Justice Department lawyers and attorneys for a group of executives with the National Labor Relations Board in Milwaukee who initiated the class action on back pay.

SEA says that those eligible for the payments will be notified next month of amounts due them; checks are to be mailed in April. Many of the executives have retired from the government or died. But retirees or their heirs are still due the same payments, based on service time and salary, as current members of the service.

Pay for SES members, which ranges from $61,296 to $72,300 a year, isn't affected, but in some cases pensions will be increased slightly.