Montgomery County lost more than $30,000 in interest over the last two years, according to a county auditor's examination, because Sheriff James A. Young did not promptly transfer money collected by his office to the county treasury.

The audit, developed at the request of the County Council, concluded that Young failed regularly to turn over to the county's general fund, as the law requires, about $200,000 in fees dating back to 1979. If the funds had been properly handled and invested, the auditors said, the county could have earned $30,000 to $35,000 in interest income.

"We feel the situation is now under control," Finance Director Albert W. Gault wrote in a memorandum accompanying the report. "We plan to monitor this activity to ensure compliance with the new procedure, which provides for the transfer of money daily to the Department of Finance."

Tony Fisher, who is challenging Young for the Democratic nomination for sheriff, called for the investigation last March, charging there were costly errors in Young's bookkeeping system. Council member Neal Potter responded by requesting the audit.

Young, who could not be reached for comment yesterday, initially blamed the disarray of his books on Virginia Burdette, his chief bookkeeper, who retired on disability in April 1981. Burdette has consistently denied that her illness contributed to the faulty bookkeeping.

Fisher said yesterday the auditor's report substantiates his charge of serious mismanagement in the sheriff's department and "provides empirical evidence of waste in the county government."