Category: Claims fundamentals · Reviewed by Chrissie Anderson, Client Executive · Last reviewed 2026-06-11
The date of loss is the calendar date on which the insured event occurred, used by insurers to determine which policy period responds to the claim, to set the limitation clock and to allocate the claim to the correct accounting and reserving period.
Category: Claims fundamentals Also known as: Loss date, date of occurrence, incident date Related concepts: Loss event, Date of discovery, Date of notification, Claim made
The date of loss is the date on which the loss event occurred — the moment the fire broke out, the collision happened, the theft took place, the injury was sustained, the financial loss crystallised. It is the temporal coordinate of the insured event, and for occurrence-based policies it is the principal determinant of whether and how the policy responds.
For most claims, the date of loss is straightforward. The fire occurred on 14 February. The collision occurred on 23 May at 14.30. The theft was discovered on 7 August, but CCTV shows the intruders entering at 02.14 on 5 August. In each case, a discrete moment can be identified.
For other claims, the date of loss is genuinely uncertain. A slow water leak may have begun weeks before discovery. A latent defect may have caused damage gradually. A long-tail disease such as mesothelioma may result from exposure decades earlier but only manifest as illness much later. In these cases, ascertaining the date of loss is itself a technical and legal exercise.
The date of loss has several functions. First, it determines which policy responds: occurrence-based policies respond to losses occurring within the policy period. Second, it sets the limitation clock for the insured’s contractual rights and for third-party rights against the insurer. Third, it determines the accounting period to which the claim is allocated for reserving and reporting purposes. Fourth, it bears on the application of policy excesses, deductibles, limits and conditions that may have changed at renewal.
The date of loss is distinguished from the date of discovery (when the insured first became aware) and the date of notification (when the insurer was informed). These three dates can be widely separated.
The legal significance of the date of loss is rooted in the contract: the policy responds to losses occurring within the period of insurance. The policy schedule will specify the inception date and the expiry date of cover; losses on or between these dates are within cover, subject to other terms.
For occurrence-based policies, the leading question is when the loss “occurred”. In Bolton MBC v Municipal Mutual Insurance Ltd [2006] EWCA Civ 50 and the subsequent Trigger Litigation (Durham v BAI (Run Off) Ltd [2012] UKSC 14), the courts considered whether the relevant occurrence for mesothelioma was the inhalation of asbestos fibres (causation theory) or the manifestation of the disease (manifestation theory). The Supreme Court in Durham held, in the policy wording before it, that the trigger was exposure.
For property losses, the position is generally simpler: the date is when the physical damage occurred. For gradual losses, the date may be a range, and courts have apportioned losses across multiple policy years where appropriate.
Limitation is governed by the Limitation Act 1980. For breach of insurance contract, the limitation period is six years from accrual of the cause of action (Limitation Act 1980, section 5). For personal-injury claims against the insurer (under the Third Parties (Rights against Insurers) Act 2010), the limitation period is three years from when the cause of action accrued or knowledge was acquired (Limitation Act 1980, section 11). The date of loss is often the starting point for these calculations.
For marine claims, the Marine Insurance Act 1906, section 60, defines constructive total loss and sets the framework within which the date of loss must be ascertained.
For consumer claims, the FCA’s ICOBS 8 and the Financial Ombudsman Service apply principles of fairness, which can extend cover to losses where the precise date is uncertain, provided the loss is otherwise within scope.
In claims handling, the date of loss is captured at FNOL. For most personal-lines claims, the policyholder can state the date precisely. For commercial claims, the broker captures the date from the insured. For some claims, the date is initially recorded as a range (for example, “between 18 and 22 December 2025”) and refined as investigation proceeds.
The handler verifies the date against the policy schedule. If the date falls outside the period of insurance, coverage is in issue. If the date falls within a different policy period covered by a different insurer, the claim may need to be transferred. If the date spans a renewal (for example, a slow leak that began under last year’s policy and continued into this year’s), apportionment may be needed.
Where the date is genuinely uncertain, several approaches are used. Best evidence: photographs, witness statements, CCTV, weather records, maintenance logs, neighbour evidence. Expert evidence: surveyors, engineers, scientific specialists who can date damage from physical examination. Inferential reasoning: working back from discovery using known characteristics of the cause.
For long-tail liability, special rules apply. The Third Parties (Rights against Insurers) Act 2010 governs how injured parties can claim directly against insurers of insolvent insureds. For mesothelioma, the Mesothelioma Act 2014 supplements the position with a statutory scheme.
For business interruption losses, the date of the underlying physical damage is the date of loss; the BI element is calculated as the loss flowing from the damage during the indemnity period. The FCA Test Case (Arch Insurance) addressed difficult questions about the date and causation of COVID-19 BI losses.
In multi-year policies and policies with continuous cover, the date of loss within a policy year is identified for reserving and accounting purposes even where cover continues uninterrupted across years.
Several variations of the “date of loss” concept arise. Date of occurrence is the standard formulation in occurrence-based policies. Date of accident is used in motor and personal-accident policies where the trigger is the accident itself. Date of damage is used in property policies emphasising the moment physical harm occurred. Date of injury is used in personal-injury claims.
Date of cause is sometimes used to mean the date the causal act or omission occurred, distinct from when the consequences manifested. In professional negligence, the date of cause is often the date the negligent advice was given, while the loss may not crystallise until much later.
For claims-made policies, the date of loss in the traditional sense is less central; the trigger is the making of the claim. However, the date of the underlying act, error or omission remains relevant for retroactive date provisions and for exclusions of prior known matters.
For batch losses (defective products, mis-sold financial products), the date of loss may be defined as the date of first manifestation, the date of supply, or the date the underlying conduct ceased. The wording matters because the cover under different annual policies may differ in limit, terms or excess.
For constructive total loss in marine, the date may be the date the vessel was abandoned to underwriters or the date of the casualty.
A small accountancy firm, North & Co LLP, holds professional indemnity insurance on a claims-made basis with insurer A for the 2024/25 policy year and with insurer B for the 2025/26 year, with renewal on 1 April. On 4 May 2026 a former client makes a claim alleging negligent tax advice given in October 2023.
There are several relevant dates. The date of the act, error or omission is October 2023 — when the alleged negligent advice was given. The date of damage may be late 2023 when the client filed the tax return based on the advice. The date of discovery by the client is March 2026, when HMRC issued an assessment. The date the claim was made against the firm is 4 May 2026. The date the firm notified its broker is 6 May 2026. The date the broker notified insurer B is 7 May 2026.
Because the policy is claims-made, the date the claim was made is the critical trigger date: 4 May 2026, within insurer B’s 2025/26 policy year. Insurer B accordingly is on cover, provided no exclusion applies. The retroactive date in insurer B’s policy is 1 April 2018, before the alleged 2023 advice, so cover is not excluded on retroactive grounds. The firm had no prior knowledge of the matter at inception of the 2025/26 policy, so the prior-known-matters exclusion does not apply.
By contrast, for a property claim under the same firm’s separate occurrence-based property policy, the relevant date would be the date the physical damage occurred. If a flood occurred on 28 March 2026, just before renewal, insurer A’s 2024/25 policy would respond.
This entry is part of the Apex Insurance Wiki. Last reviewed by Matt Bartlett on 2026-06-11. Next review: 2026-12-11.
Apex Insurance Brokers Limited. Authorised and regulated by the Financial Conduct Authority, FRN 724952. Registered in England and Wales, Companies House 07014570. This entry provides general information about UK insurance concepts and is not regulated advice. Consult your insurance broker on your specific position.
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