The full form of IBNR is Incurred But Not Reported. It’s used on Business ,Banking in India

In insurance, incurred but not reported (IBNR) claims is the amount owed by an insurer to all valid claimants who have had a covered loss but have not yet reported it. Since the insurer knows neither how many of these losses have occurred, nor the severity of each loss, IBNR is necessarily an estimate. The sum of IBNR losses plus reported losses yields an estimate of the total eventual liabilities the insurer will cover, known as ultimate losses.

Incurred but Not Reported (IBNR) — an estimate of the liability for claim-generating events that have taken place but have not yet been reported to the insurer or self-insurer. The sum of IBNR losses plus incurred losses provides an estimate of the total eventual liabilities for losses during a given period.