Key Treasury Department managers could get bonuses of up to $5,000 this time next year under an industry-type work rating and payoff plan the giant department will begin soon.

Secretary Mike Blumenthal has approved a pilot program for his office that will have more than 700 senior level managers involved in a work planning/performance evaluation system.If it works, other federal departments may adopt it as part of the president's civil service reform program.

Treasury's plan, which must be cleared by the Civil Service Commission is aa cross between corporation bonus programs and a super-charged version of the existing federal incentive awards program. The latter has fallen into disuse in some agencies, and become routine in others. Last year, for example. Treasury gave out only $27,000 in incentive awards.

Under the Blumenthal plan, employes in grades 12 through 18 will negotiate with their bosses over work plans and goals for the coming 12-month period. After they have reached agreement, the executives will begin competing against each other-but in greater competition with themselves-to meet and exceed work goals. Bonuses of up to $5,000 will go to about 10 percent of the people in the program. Payoffs would come in October or November each year. Just like pre-Christmas bonuses in some private firms.

Initially the work planning program will be limited to the Office of the Secretary. The U.S. Customs Service (a major Treasury agency) also wants to try it in headquarters here. Eventually it could spread to other units of the department, which has 172,000 employes, and down into lower grades.

Treasury officials say the program has $150,000 to fund it. Within the next few weeks employes will be briefed on how it works. Negotiations with managers will begin on a one-to-one-basis. A group of five to seven Treasury officials, perhaps chaired by Blumenthal himself, will evaluate the executives' assignments and progress, and make the awards.

The program will cover more than 770 career and political managers in the Grade 12 through 18 range. Political appointees will have to take part in the planning-performance system, but instead of cash bonuses they will get certificates or other nonmonetary rewards.

Treasury officials say the program is an outgrowth of Blumenthal's frustration at not being able to reward-to withhold rewards-from deserving managers. "He came out of Bendix Corporation (where in five years he became chairman president and chief executive officer) where people got rewards if they did well. and lumps if they didn't," aide said.

Another Treasury staffer said Blumenthal was "horrified" when he attended a Treasury awards ceremony, where for several hours, employe were honored for a variety of accomplishments, "from top service to merly remaining alive for a given period of time. The whole thing really shook him. He asked 'isn't there a better way?' and told us to come up with one."

Although Blumenthal has a reputation as a hard-line sometimes frosty chief executive, he is in fact anxious, aides say, to pat people on the back when he feels they merit it. In one speech to a business group, Blumenthal complained he "cannot fully reward" top people "no matter how outstanding their performance . . . Salaries and fringe benefits are fixed by law. So-called 'incentive awards' are merely minor bonuses and few and far between, to boot."

Within the next couple of weeks-assuming CSC clears the Treasury plan-workers will be notified of the new system, and "negotiations" will start on future work goals.