This is one in a series of articles on President Reagan's fiscal 1986 budget proposals.

The General Services Administration would have to live with a 3.7 percent cutback -- or $14.7 million less -- under President Reagan's fiscal 1986 budget proposals.

Within GSA, the biggest reduction would be a 10 percent cut in management expenses. GSA Comptroller Raymond A. Fontaine said the $13.2 million cutback would involve reducing field operations significantly.

In one area, GSA's costs will drop because of some sleight-of-hand promoted by the Office of Management and Budget by which responsibility for maintaining headquarters buildings in Washington will be transferred to the agencies that occupy them.

OMB officials say they think agencies will be able to provide better services for less money. As a result of the change, which does not require congressional approval, the GSA budget would drop by $19.5 million.

"It's a loophole that we don't have to deal with; the Office of Management and Budget does," Fontaine said. "I'd like to keep an eye on how tight some of the other agencies will be. I think they'll spend much more than we did maintaining their space."

GSA's revolving fund to pay for leased office space would be capped at its current level, $839 million. The cap, said Ira Jekowsky of the Public Buildings Service, means that GSA will have "to work hard" to squeeze employes into less office space and to shift workers into government-owned facilities.

OMB officials rejected a GSA request for an additional $60 million to purchase new buildings in 1986. The so-called Opportunity Purchase program was set up two years ago to buy buildings available at below-market prices. GSA has allowed the program to be "emasculated by politics," Fontaine said, "so for now, it's nowhere." GSA would still have $135 million in carry-over funds available for purchases.

GSA's Office of Federal Supply and Services would get $2.6 million to continue computerizing its purchasing operations.

Under the budget, the division would save $1.8 million by contracting out additional warehouse operations.

The cost of running the National Defense Stockpile would drop $800,000, to $26 million.

But "that's a guess," GSA budget chief William B. Early said. "The administration hasn't decided on purchases or sales from the stockpile. That's a blank page in the budget."