Internal Revenue Service Commissioner Roscoe L. Egger Jr. yesterday dismissed reports of a massive shredding of tax returns in the agency's Philadelphia service center as "sheer, utter nonsense."

Anonymous calls to the office of Sen. John Heinz (R-Pa.) have charged that at least 27,000 returns have been shredded on various occasions, mostly because workers have had trouble keeping up with production standards. Press reports also have said returns were lost or hidden for the same reason.

"If any such number of returns as that were destroyed, we would know it from our accounting system. I'm here to tell you it's just nonsense," Egger told reporters. The service's investigations office has invited anyone who has knowledge of return-shredding to provide details, and "to date, no one has come forward."

Despite the installation of a problem-plagued new computer system, the IRS will be able to send refunds before the June 1 deadline to anyone who files a processible return by April 15, Egger predicted. After that, the service will have to pay 13 percent interest on the refunds it still owes. He said the agency expects to pay about $200 million in such interest this year.

All 10 regional centers are processing returns faster than they did earlier in the filing season, but nationally, processing is still behind last year's pace, Egger said.