WASHINGTON-Benefit managers beware: While most of the employee benefit-related provisions contained in tax and budget bills signed last week by President Clinton don't take effect until next year, a handful already are in force.

Perhaps the most significant-from a cost standpoint-of those provisions already in effect involves employer liability for end-stage renal disease, an impairment of the kidneys, whose annual treatment costs often are in the $50,000 range.

Under legislation enacted more than 20 years ago, Congress expanded the Medicare program to provide coverage for ESRD for people under 65, the normal eligibility age for Medicare. Legislation later was passed so that employer health care plans became the primary payer-for an 18-month period-of medical bills for employees or retirees under 65 who developed the disease.

But, effective Aug. 5, the day President Clinton signed the legislation, employers became the primary payer of medical services for 30 months for employees who develop ESRD, after which Medicare becomes the primary payer.

The new law applies to services "beginning on or after the date that is 18 months prior to enactment."

That means that employers' expanded period of being the primary payer of medical claims applies to employees who have been treated for ESRD in the past 18 months and not just to employees who develop ESRD after the legislation was signed into law, said Frank McArdle, a consultant with Hewitt Associates L.L.C. in Washington.

For example, if an employer had been the primary payer for the past five months for an employee with ESRD, that company would continue to be the primary payer for an additional 25 months.

However, employers would not resume liability for employees with ESRD whose 18 months of employer-provided coverage had been reached prior to the enactment of the law.

The tax bill also retroactively reinstates the tax-favored status of employer-provided educational assistance benefits. Section 127, under which employers could reimburse employees tax-free for up to $5,250 in undergraduate educational expenses, expired June 30. But the new law reinstates Section 127 through May 31, 2000.

The law, also effective Aug. 5, eliminates the requirement that employers file copies of summary plan descriptions and summaries of material benefit modifications with the Labor Department. The department, though, still can request copies of those documents, which still must be furnished to employees.

In addition, the law permanently continues the Medicare Data Match Program. Under this program, the Health Care Financing Administration-the federal agency that administers Medicare-reviews employees' health care coverage and claims to see if employers' health care plans should have paid the claims rather than Medicare.

Typically, overpayment situations involve employees who stay on the job after 65-the year they are first eligible for Medicare-and hospitals that incorrectly bill Medicare rather than the older workers' employers or health insurer. Back in the early 1980s, Congress shifted to employers and away from Medicare the primary responsibility of paying medical bills of employees who stay on the job after 65.