Even though the Social Security Administration does not expect the Year 2000 computer glitch to disrupt January benefit payments to about 44 million Americans, the agency appears to be leaving nothing to chance.

Social Security Commissioner Kenneth S. Apfel said yesterday that the computer tapes used for January's direct-deposit payments to banks have been checked, certified for accuracy and sent to the Treasury Department. The direct-deposit payments will be transmitted to banks on the morning of Dec. 30 for credit to accounts on or before Jan. 3.

In addition, Apfel said, paper checks will be delivered to the U.S. Postal Service a day early next week to give it extra time to sort the envelopes and prepare them for delivery on Jan. 3, the day most Social Security recipients are scheduled to get their next monthly payment.

"The people that depend on us can rest assured that their payments will arrive on time. In other words, our customers can rely on us in January just as they have for over 60 years," Apfel said.

Social Security has been working on the Year 2000 computer problem, known as Y2K, since 1989, making it one of the first agencies to discover the "millennium bug." Computers using two-digit date systems may misinterpret "00" as 1900, not 2000, and shut down or otherwise malfunction.

Apfel said Social Security has spent $48 million reviewing 308 "mission critical" computer systems and more than 35 million lines of computer code. The agency also tested almost 2,000 data exchanges with state governments, the Internal Revenue Service, the Treasury Department and the Federal Reserve.

Social Security relies on electronic payments to deliver benefits. More than 75 percent of Social Security recipients get their benefits electronically through direct deposit. The agency's vast computer systems process 22 million program transactions daily.

Since October 1998, Social Security and the Treasury Department have been making benefit payments using Year 2000-compliant software. The Federal Reserve also included Social Security transactions in its Y2K tests with banks and financial institutions.

In the unlikely event that the first benefit payments next year are delayed--because of either bad weather or computer woes--Social Security has devised an emergency plan to get money to recipients facing economic emergencies.

The nearly 1,400 Social Security field offices across the country will be authorized to hand out checks for as much as $999 to people facing financial hardship, Apfel said. Extra operators will be on duty to handle telephone calls in case of problems.

As a precaution to protect its computers from electric power surges, just before midnight Dec. 31, Social Security's main data center near Baltimore will switch to jet fuel generators. The agency will turn off the generators when "the power company notifies the agency that everything is fine," Apfel said.

After midnight, computer specialists will again test the agency's systems to ensure they will process transactions for 2000. Throughout New Year's Day, agency managers will go to field offices and inspect equipment and report their findings to regional offices, which will forward data to a command center near Baltimore, Apfel said.

The Y2K weekend comes at an especially crucial time for Social Security. The first week of the year is one of the agency's busiest times. Newly retired Americans often file for benefits then and the agency usually handles more telephone inquiries, because cost-of-living increases show up in the year's first check.

Although the agency has a remarkably low error rate--about 4,000 checks delayed or inaccurate because of routine computer glitches out of 44 million monthly payments--Apfel said Y2K will likely challenge Social Security's ability in the first week to sort out Y2K errors from the day-to-day snarls.

But, he said, "the bottom line is that we're ready. . . . Even though the century will change, our dependability won't."

CAPTION: Social Security Commissioner Kenneth S. Apfel said benefit recipients can "rest assured" they will get their January checks and direct deposits on time.