Private care homes claimed public fees for a small number of dead residents for around two years, an Audit Office report in Northern Ireland has said.
The health trust which paid for the services failed to pick up the fraud earlier because of how it selected cases for investigation, comptroller and auditor general Kieran Donnelly's office said.
Over-payments of around £100 per week were made but they represented only a handful of cases out of nearly 12,000 residential and nursing home care packages registered in Department of Health statistics last year.
The sum totalled around £35,000 and involved three residents and different homes. The money was recovered after data was matched as part of the National Fraud Initiative (NFI).
Mr Donnelly said: "Preventing and detecting fraud is an essential part of public business, to help ensure that limited funds for the provision of goods and services are properly directed to where they are needed and not siphoned off by fraudsters.
"Fraud is not a victimless crime; we all pay the price."
His report - The National Fraud Initiative: Northern Ireland - examined the matching of information between different public bodies to try to reduce the level of over payment.
The NFI matches health trusts' private care home payments records to death registers.
A data match showed that a resident whose care was paid for by a trust died in December 2014.
The match appeared in a previous anti-fraud exercise but, because of the methodology used by the trust to select cases for investigation, the error was not picked up.
The Audit Office report said: "In the intervening period the care home did not notify the change of circumstances and payments continued until early 2017."
The care home was overpaid by £11,229.
The trust which paid the money has recovered the full amount.
It is reviewing contract management arrangements and its methodology for sampling potentially fraudulent matches.
A second health and social care trust detected two cases relating to the same care home.
The residents died in May 2014 and June 2015.
The care home did not indicate the change of circumstances and the trust continued to pay fees of £100 per week in each case, until it became aware of the deaths in early 2017 through NFI data matches.
Resulting over-payments totalled £24,000. All the money has been recovered.
The trust has tightened its procedures in relation to non-returned payments, the Audit Office said.