Congressional County Club was underbilled by $10,000 for liquor it bought from Montgomery County's Department of Liquor Control in 1976 and the error went undetected by the county for almost five years until it was uncovered during a grand jury probe, County Finance Director Albert Gault said yesterday.

The money has now been paid in full, and county prosecutor Andrew Sonner said investigators found no evidence of criminal wrongdoing. County officials blamed a faultily programmed county computer in explaining why the club was billed only $1,767.25 for liquor worth $11,767.25 delivered in connection with the Professional Golfers Association (PGA) tournament held at Congressional in July 1976.

The club apparently discovered the mistake within a short time and tried to pay the additional $10,000, but county bookkeepers mistakenly applied the amount to pay in advance for beer the club later purchased, Gault said.

Disclosure that a $10,000 under-payment went undetected for almost five years comes at a time when the liquor department is under fire for allegedly poor management. A county grand jury recently completed a seven-month probe of allegations of bribery in the liquor department but brought no indictments.

The department's current deputy chief, Frank Orifici, who in 1976 was a liquor salesman for Schenley Industries, with the Congressional club as one of his clients, said he was asked to help supervise a special liquor inventory bought for the tournament and did so. Charles Buscher, then a Schenley executive, was at the time serving on the tournament-planning committee.

Both Buscher and Orifici are major figures in the year-old controversy over the county's $75-million-a year liquor department, which holds a monopoly on liquor sales in the county.Orifici said he learned of the underpayment only when the grand jury discovered it. Buscher said he knew nothing of it when a reporter called on Tuesday.

Last week, Buscher disclosed publicly hat in January 1980 he had made a $2,000 personal loan to Gerard Evans, then a close aide to Montgomery County Executive Charles Gilchrist. At the time the loan was made, Evans was recommending Orifici, who is married to Buscher's niece, for his current job as department deputy head.

Earlier this week, state prosecutors announced plans to investigate the loan. Republican officials, meanwhile, have asked the state investigators to look into other aspects of liquor department operations and for federal prosecutors to enter the case. County Executive Gilchrist and all members of the County Council are Democrats.

The shortage in the club payment grew out of a 232-case order of liquor delivered to the club in July 1976. A computer-prepared invoice showed the total cost as $1,767.25, even though columns on the form actually add up to $11,767.25, according to C. H. Bartz of the county's Division of Accounting, which processes liquor bills. The computer was not programmed to handle sums of $10,000 or more and apparantly lopped off the left digit "1," Bartz said.

Three weeks later Congressional, apparently having discovered the error, sent the county government a check for $21,831.78 -- a sum that covered outstanding bills and the additional $10,000 the club in fact owed, Bartz said. But county accountants checking their own, incorrect books concluded that Congressional actually owned $10,000 less than that sum.

So the accountants deposited the "excess" $10,000 to a second beverage account the club maintained, this one holding advance payment for beer orders.

Bartz said that the club drew down the overpayment in following months with new beer orders. The $10,000 still owed for the 1976 liquor shipment only came to light when grand jury investigators pored over department records this past winter.

Their questions later led the department to rebill the country club, which mailed a check for $10,000 last Feb. 27, according to Bartz.

Officials of the country club could not be reached for comment yesterday.