An employee at the Belfast Health Trust was paid almost £84,000 in wages after leaving the job.
An investigation has been launched after the person was left on the books, the trust confirmed.
The matter was highlighted in a theft and fraud report.
The report said: "Although uncommon, this case highlights the importance of ensuring that there are robust procedures in place for removing staff from the payroll and the need for cost centre managers to review budget reports to ensure salaries paid are appropriate and correct.
"Other additional controls include reconciliations between personnel and payroll details and the review of payroll procedures by internal audit to confirm the adequacy and effectiveness of control systems."
The investigation will determine whether the case involved any wrongdoing.
The report, Annual Theft and Fraud Report 2009/10, added that £102,000 of pay and pay-related cases were noted.
"One case in particular accounted for almost £84,000 of this total value and relates to an employee who continued to be paid after they left the organisation's employ," it said.
It said there were 177 cases of actual, suspected and attempted fraud reported to the Department of Finance and Personnel. This is a decrease of 13 cases from the level reported for 2008/09.
Part of the decrease in the number of cases reported may be attributed to the fact that cases of pension fraud, where payments were being made to a deceased person, are not included in the 2009/10 figures.