THE ARMY GUARD AND RESERVE PAYROLL IS ABOUT $1.3 BILLION. MANAGEMENT CONTROLS OVER THIS PAYROLL AND RELATED PERSONNEL SYSTEMS ARE NOT ADEQUATE TO PREVENT ERRONEOUS PAYMENTS. INACCURATE DRILL ATTENDANCE RECORDING AND REPORTING BY GUARD AND RESERVE UNITS AND INADEQUATE ERROR DETECTION PROCEDURES AT PAYROLL PROCESSING STATIONS ARE RESULTING IN ERRONEOUS PAYMENTS FOR DRILLS NOT ATTENDED, PAYMENTS FOR THE SAME PERIODS OF TRAINING, OR PAYMENTS BY BOTH THE ACTIVE ARMY PAY SYSTEM AND GUARD AND RESERVE PAY SYSTEMS. IN ADDITION, VITAL PERSONNEL STRENGTH INFORMATION MAINTAINED IN THE PAY AND PERSONNEL SYSTEMS IS FREQUENTLY INCONSISTENT, INACCURATE, AND CAN ADVERSELY AFFECT BUDGET AND MOBILIZATION PLANS. THE RELIABILITY OF THE INFORMATION IN THE PAY AND PERSONNEL SYSTEMS IS QUESTIONABLE PRIMARILY BECAUSE DATA ARE NOT UPDATED IN A TIMELY MANNER, OR INFORMATION IS LOST, REJECTED, OR ERRONEOUSLY CHANGED. GAO RECOMMENDS THAT THE ARMY RECONCILE PAY AND PERSONNEL DATA VITAL TO MANAGEMENT NEEDS; DEVELOP PROCEDURES TO IMPROVE THE TIMELINESS, FLOW, AND ACCURACY OF SOURCE DATA; AND DEVELOP PROGRAMS TO VERIFY OR CORRECT INFORMATION AS THE NEED ARISES. OFFICIALS AT THE ARMY INSTALLATIONS REVIEWED GENERALLY AGREED WITH THE FINDINGS. (AUTHOR ABSTRACT MODIFIED--RCB)