Known Loss Rule
Also known as: Loss in Progress, Known Loss Doctrine, Loss in Progress Rule
The known loss rule — also called the loss in progress doctrine — holds that you cannot buy insurance for a loss that has already happened or that you already know is happening when the policy begins. It flows directly from the fortuity principle: insurance exists to transfer uncertain risk, so a claim the insured knew about at inception falls outside the coverage grant. Courts apply it even when a policy has no explicit exclusion, treating known losses as fundamentally uninsurable rather than merely excluded.
For a small-business owner, the rule is a compliance and honesty issue at renewal or when switching carriers. If you become aware of a defect, an injury, or a circumstance likely to produce a claim, you generally cannot wait, buy a new policy, and then present the loss as if it were fresh. This is especially important with claims-made policies, where applications ask whether you know of any facts that might reasonably lead to a claim — misrepresenting that knowledge can void coverage. Being candid protects you, because a properly disclosed prior circumstance may still be covered under the outgoing policy.
The practical nuance is the difference between knowing of a loss and merely being aware of general risk. Ordinary awareness that lawsuits happen in your industry does not trigger the rule; specific knowledge of an actual loss or a substantially certain one does. Timing tools like the retroactive date and continuity provisions interact with this rule to define which policy period owns a claim. When in doubt, report circumstances to your current carrier before they mature into claims, rather than assuming a future policy will pick them up.
The standard ISO Commercial General Liability form (CG 00 01) codifies this in its Coverage A “known injury or damage” provision, granting coverage only if no insured knew the harm had occurred before the policy period.
Real-world scenario
Meridian Architects LLC, a 12-person design firm, carried a claims-made professional liability (E&O) policy with a $2,000,000 per-claim limit, a $4,000,000 aggregate, a $25,000 deductible, and an $18,000 annual premium. In March, while finishing construction documents for a $310,000 hospital-wing commission, Meridian's principal received an email from the project's structural engineer flagging a load-calculation error and estimating roughly $640,000 in remediation if the framing was built as drawn. The principal quietly asked the engineer to keep working on a fix.
In May — with renewal approaching — Meridian shopped the coverage and bound a cheaper policy for a $14,500 premium (a $3,500 saving) effective June 1, but the application never disclosed the known design error. When the hospital's contractor discovered the defect and filed a formal demand in September seeking the full $640,000, plus $48,000 in delay costs, Meridian tendered the claim to its new carrier. The insurer invoked the known loss rule: because the principal had actual knowledge of the loss before the $14,500 policy incepted, the event was not fortuitous under the fortuity principle, and the carrier issued a formal coverage denial.
Meridian was left self-funding the fight — $95,000 in defense counsel, a $450,000 settlement, and $12,000 in expert engineering fees, roughly $557,000 out of pocket against a business that had tried to save $3,500. Had the firm reported the matter to its original insurer before switching, that carrier's $2,000,000 limit (net of the $25,000 deductible) would very likely have responded. The lesson: a policy's retroactive date and disclosure duties exist precisely to keep already-known losses out of a new insurer's book.
How it affects your premium
The known loss rule is an underwriting and coverage doctrine rather than a line-item charge, but several factors determine how aggressively an underwriter probes for known losses — and how those answers move your premium, deductible, or eligibility:
- Prior-acts / retroactive-date span: The further back a policy reaches (see prior acts coverage), the more incidents an insured might already know about, so underwriters load the rate or tighten disclosure warranties.
- Application warranty statements: Signed "no known claims or circumstances" attestations let insurers rescind or deny later; firms that leave these blank or hedge them are surcharged or declined.
- Claims-made vs. occurrence structure: Claims-made lines police known losses through the reporting trigger and continuity date, which shapes both price and the questions asked at binding.
- Loss-run and continuity history: Gaps in coverage or a fresh carrier relationship raise suspicion that a loss is being shifted onto the new policy, pushing rates up.
- Industry claim latency: Professions with slow-emerging losses (design, legal, medical) get heavier known-loss scrutiny than short-tail trades, affecting deductible minimums.
- Quality of internal controls: Documented QA, peer review, and incident-logging practices reassure underwriters and can earn credits.
- Circumstance-reporting behavior: Insureds who promptly notice potential circumstances to their expiring carrier avoid the known-loss trap and preserve favorable renewal terms.
Common misconceptions
Myth: If a claim is not officially filed until after my new policy starts, the known loss rule cannot apply.
Reality: What matters is knowledge, not the filing date. If you knew about the loss or the circumstance likely to produce it before inception, an insurer can deny even a claim served months later — which is why prompt first notice of loss to your current carrier matters.
Myth: The known loss rule only comes up on claims-made policies like E&O.
Reality: It applies across property, liability, and occurrence policies too; any insurer can contest coverage for a loss that was already in progress or known when the policy took effect.
Myth: Buying insurance the day after a fire or lawsuit surfaces just means my claim will be a little slower to pay.
Reality: It usually means no payment at all. Insuring a loss you already know has happened defeats the fortuity requirement, and the carrier will deny the claim outright and may rescind the policy.
Frequently asked questions
What exactly is the known loss rule?
How is the known loss rule different from a policy exclusion?
Does the known loss rule apply to D&O and cyber policies?
How do I avoid triggering the known loss rule when I switch carriers?
If my old policy was in force when I first learned of the problem, am I protected?
Sources cited
Need known loss rule coverage?
Compare quotes from 10+ commercial insurance carriers in 5 minutes. Free, no contact info required.
Get My Quotes →