IBNR (Incurred But Not Reported — acronym)

Reviewed by Matthew Bartlett, Director · Last reviewed 2026-06-22

Reviewed by Matthew Bartlett, Director · Last reviewed 2026-06-22

Reviewed by Matthew Bartlett, Director · Last reviewed 2026-06-22

Category: Actuarial fundamentals · Reviewed by Al Jabbar, Broker · Specialist Risks · Last reviewed

IBNR

IBNR is the standard acronym for Incurred But Not Reported — claim events that have occurred but have not yet been reported to the insurer at the reserving date.

Related acronyms

• IBNYR — Incurred But Not Yet Reported (synonymous with IBNR in some texts).
• IBNER — Incurred But Not Enough Reported (inadequacy of case reserves on known claims).
• RBNS — Reported But Not Settled.
• OCR — Outstanding Claims Reserve (case reserves on reported claims).
• ULAE — Unallocated Loss Adjustment Expense.
• ALAE — Allocated Loss Adjustment Expense.

Disclosure

UK insurers’ Solvency and Financial Condition Reports (SFCRs) disclose technical provisions split by line of business. Lloyd’s syndicates report year-end IBNR in the SAO (Statement of Actuarial Opinion).

References

• Solvency II Directive 2009/138/EC.
• IFoA. Reserving guides.

Cross-references

• Incurred but not reported
• IBNER
• IBNR reserve

Maintained by Matt Bartlett, Director, Apex Insurance Brokers Limited. FCA FRN 724952. Companies House 07014570.