The Supreme Court agreed yesterday to resolve what the government calls a "major question" about how the Internal Revenue Service conducts investigations for possible tax fraud.

In 1976 alone, the IRS, Intelligence Division conducted 8,797 full-scale investigations of tax fraud recommended prosecution in 2,037 cases.

The "major question" arose from a seven-year-old Supreme Court decision that an IRS summons to a third party "may be issued in aid of an investigation if it is issued in good faith and prior to a recommendation for criminal prosecution."

Federal appellate courts have interpreted teh decision in conflicting ways, creating what the Justice Department terms "disaray" about the use of a summons for what is or may become a criminal investigation.

In the case at issue, the third party as the LaSalle National Bank of Chicago. It declined to comply with an IRS summons for records wanted by Special Agent John F. Olivero for an investigation of a man named John Gattuso.

Federal Judge Frank J. McGarr ruled against the IRS, holding that Olivero wanted the bank records "solely for the purpose of unearthing evidence of criminal conduct" by Gattuso and consequently hadn't complied with the "good faith" requirement of an earlier court ruling. McGarr didn't credit Olivero's claim that he alos was pursuing a civil investigation.

The Seventh Circuit U.S. Court of Appeals affirmed. Ruling that the IRS had issued the summons solely in aid of a criminal investigation.

In a brief urging Supreme Court review, Solicitor General Wade H. McCree said there was no basis for the appellate court's finding that at least in his own mind. Olivero, at all times, was conducting an exclusively criminal inquiry.

McCree also said that was "no occasion" for Judge McGarr to reject the credibility of Olivero's testimony.

"The Court of Appeals" ruling that an agent's subjective motive can be taken into account in determining whether a summons is issued in 'good faith' threatens to impair the enforcement of the internal revenue laws," McCree said.

"In any investigation conducted by a special agent of the IRS, the focus of the inquiry is to ascertain whether there is any evidence of criminal conduct, but that inquiry also necessarily involves questions of civil tax liability," McCree said.