Discrepancies of some £435,000 have been found in the revenues and benefits accounts of the former Blyth Valley BC.
Northumberland County Council auditors are trying to discover whether it is technically possible to reconcile results from two IT systems used to establish whether any loss occurred.
The problem began when Blyth Valley replaced its Pericles system just before its March demise with the Northgate system used by the county’s other councils.
There is no suggestion that either malfunctioned, but officers cannot compare their results.
A report to Northumberland’s audit committee said: “Although the systems agree in total, once any degree of ‘drill-down’ is undertaken, there are significant differences in the balances within each category.”
It said the arrears totals differed by £181,000, benefits by £108,000 and excess benefit by £146,000.
The total of homes in each council tax band agreed between the two systems, but, for example, there were inexplicable differences in exempt and single person household records. Northgate showed no second or long-term empty homes, while Pericles indicated 128, the report said.
It explained: “It is quite possible that allocating codes correctly against the correct items would rectify much of the problem. However, there is no obvious mapping which would deliver this result.”
Steven Mason, Northumberland’s resources director, said: “It is frustrating that this has happened as it is consuming audit resources, and it’s a priority to sort it out by the end of August.”