Federal retirees, including 100,000 in this area, won't be getting that 3.1 percent cost-of-living raise they had expected in their January checks.

Office of Personnel Management officials confirmed yesterday that they have found a way to remove most of the raises from computer tapes that had already been prepared to issue the January checks. The Treasury Department will begin printing checks during the weekend to mail to nearly 2 million retirees and survivors.

The 3.1 percent raise, which was to have been in effect for only one month, would have amounted to about $28 for the typical retiree, and about half that amount for widows or widowers of retirees.

The COLA was a sure thing until a couple of weeks ago, when congressional Democrats proposed eliminating it to prepare the deficit-reduction package that became law this week. The original proposal in the budget-cutting package presented by congressional Republicans was to freeze retiree COLAs beginning in 1987, but to allow the raises this year.

When it became apparent that the Gramm-Rudman- Hollings amendment might pass Congress, the Office of Personnel Management said it could cancel the raises starting with February checks. But OPM warned that taking the raise out of checks already programmed for January would cause major overpayments and underpayments, and political problems for the administration.

Despite OPM's warning, the administration and congressional leaders told the agency to find a way to begin the retiree COLA freeze immediately. OPM officials say they have come up with a computer program that will cancel the raise for about 95 percent of the people getting checks next month.