Written by Justin Goodman, CIC, CLCS, CISC, CEO and Co-Founder, Total CSR Published: August 26, 2026 · Last reviewed: August 26, 2026
In plain language: A cause of loss form is the part of a commercial property policy that spells out which disasters or events, like fire, windstorm, or theft, the insurance company will actually pay for. Without it, the base policy has no list of covered perils.
Technical definition: A cause of loss form is an ISO endorsement attached to a commercial property coverage form (such as CP 00 10) that defines covered perils. Three standard versions exist: Basic (CP 10 10), Broad (CP 10 20), and Special (CP 10 30), each expanding the scope of triggering events and applicable exclusions.
Cause Of Loss Form at a Glance
| Attribute | Detail |
|---|---|
| Also known as | Causes of Loss Form, Peril Form |
| Category | Property policy endorsement |
| Lines of business | Commercial Property, Businessowners Policy (BOP) |
| Industries most affected | Retail, Manufacturing, Real Estate, Hospitality, Construction |
| Related forms or endorsements | CP 10 10 (Basic), CP 10 20 (Broad), CP 10 30 (Special), CP 00 10 |
| Who bears the risk | Property owner or tenant if the loss event is not a covered cause |
| Common solution | Attach Special Causes of Loss Form for broadest, open-perils protection |
| Also interacts with | Building and Personal Property Coverage Form, exclusions, endorsements adding back excluded perils |
Key Takeaways
- A cause of loss form is the endorsement that lists the specific perils a commercial property policy will pay claims for.
- Agencies must confirm which version, Basic, Broad, or Special, is attached, because each one changes what a client actually has coverage for after a loss.
- The most common pitfall is assuming “Special” means “all-risk” with no exclusions, when in fact water damage, flood, earth movement, and other perils are still excluded and require separate coverage.
- A quick win is to always request the declarations page and the actual attached cause of loss form number during account setup, rather than relying on the policy’s marketing name.
On This Page
- What Is Cause Of Loss Form in Insurance?
- How Does Cause Of Loss Form Work?
- Real Claim Examples Involving Cause Of Loss Form
- Cause Of Loss Form vs. All-Risk Policy: What Is the Difference?
- What Are the Most Common Mistakes With Cause Of Loss Form?
- How to Explain Cause Of Loss Form to a Client
- Frequently Asked Questions About Cause Of Loss Form
- Related Insurance Terms
- Sources and References
- About the Author
What Is Cause Of Loss Form in Insurance?
Cause of loss form is the mechanism that turns a commercial property coverage form from an empty shell into an actual promise to pay. The base ISO Building and Personal Property Coverage Form (CP 00 10) does not list covered perils on its own; it relies on an attached cause of loss form to define the scope of the peril insuring agreement. This structure exists so carriers can offer the same base form to different risk classes while dialing coverage breadth up or down through the attached endorsement.
The doctrine behind this split traces to how property insurance has historically been sold: named-peril policies list specific covered events, while open-perils (sometimes called “all-risk”) policies cover everything except what is specifically excluded. ISO’s three standard forms mirror that spectrum. The Basic form (CP 10 10) covers a short list including fire, lightning, explosion, and vandalism. The Broad form (CP 10 20) adds perils like falling objects, weight of ice and snow, and water damage from plumbing. The Special form (CP 10 30) flips the structure entirely, covering all direct physical loss unless specifically excluded.
Consider a warehouse owner whose roof collapses under heavy snow load. Under a Basic form, weight of ice and snow is not listed, so the claim is denied. Under a Broad or Special form, that same peril is covered, assuming no applicable exclusion like faulty construction defeats it. The cause of loss form attached to the policy, not the coverage form itself, determines the outcome.
How Does Cause Of Loss Form Work?
- The policy issuance. The carrier attaches a specific cause of loss form, Basic, Broad, or Special, to the base commercial property coverage form at the time the policy is written.
- The loss event. A covered property sustains physical damage from an event such as fire, wind, theft, or water intrusion.
- The peril check. The claims adjuster reviews the attached cause of loss form to determine whether the triggering event falls within the listed perils (Basic or Broad) or is not among the form’s specific exclusions (Special).
- The exclusion analysis. The adjuster checks for standard exclusions that apply regardless of form version, such as flood, earth movement, or nuclear hazard, since these typically require separate policies or endorsements.
- The coverage determination. The claim is approved, denied, or partially paid based on whether the cause of loss form’s peril language and exclusions support the specific facts of the loss.
Real Claim Examples Involving Cause Of Loss Form
Warehouse roof collapse under snow load
A distribution center in the Midwest suffered a partial roof collapse after a heavy snowstorm. The policy carried the Basic Causes of Loss Form (CP 10 10), which does not include weight of ice, snow, or sleet as a covered peril. The claim was denied, and the client absorbed over $180,000 in structural repair costs because the agency had not upgraded the account to the Broad or Special form at renewal.
Theft of inventory from a retail stockroom
A boutique retailer experienced a break-in with significant inventory loss. The policy carried the Special Causes of Loss Form (CP 10 30), which covers theft as an open peril subject to standard exclusions. The claim was paid in full after the adjuster confirmed no applicable exclusion, such as inventory shortage discovered only through inventory computation, applied to the facts.
Water damage from a burst pipe in a leased office
A professional services tenant discovered water damage after a supply line froze and burst over a weekend. The Broad Causes of Loss Form (CP 10 20) attached to the BOP specifically includes accidental discharge of water from plumbing systems. The claim was approved, but the adjuster applied a separate policy exclusion for damage occurring while the building was unoccupied beyond the policy’s specified time limit, reducing the payout.
Cause Of Loss Form vs. All-Risk Policy: What Is the Difference?
Cause of loss form refers to the specific ISO endorsement (Basic, Broad, or Special) attached to a commercial property policy that defines covered perils, while all-risk policy is a broader industry term, now more precisely called open perils coverage, describing any policy structured to cover all causes of loss except those excluded. The Special Causes of Loss Form is the ISO mechanism that actually creates open-perils coverage within a standard commercial property policy.
| Comparison area | Cause Of Loss Form | All-Risk Policy |
|---|---|---|
| Primary use case | Defines peril scope within an ISO commercial property policy | Describes any policy using open-perils structure |
| Coverage / concept type | Specific endorsement (CP 10 10, 10 20, or 10 30) | General coverage philosophy or marketing term |
| Typical exclusions | Varies by version; Special form has the fewest peril limitations | Depends entirely on the underlying policy’s exclusion list |
| Who is most affected by errors | Property owners denied claims for perils not listed in Basic or Broad forms | Insureds who assume “all-risk” means no exclusions exist |
| Common mistakes | Confusing form version without checking the actual attached endorsement | Treating “all-risk” as a synonym for “no exclusions” |
What Are the Most Common Mistakes With Cause Of Loss Form?
- Agencies quote a policy as “all-risk” without confirming the Special Causes of Loss Form is actually attached, leading to client confusion when a claim is denied under a lesser form.
- Producers assume Broad and Special forms are interchangeable, but Broad still operates on a named-peril basis and excludes many perils Special would cover.
- Renewal reviews skip verifying whether the cause of loss form changed between policy terms, which can silently downgrade a client’s coverage without anyone noticing.
- CSRs fail to explain that even the Special form excludes flood, earth movement, and other perils requiring separate policies, creating a false sense of complete protection.
- Files are documented with the coverage form number but not the attached cause of loss form number, making it difficult to confirm what was actually bound if a dispute arises.
How to Explain Cause Of Loss Form to a Client
Explaining Cause Of Loss Form to a personal lines client
Your homeowners policy works a little differently, but think of it like a list of what’s covered when something goes wrong at your home. Commercial property policies use a similar list, called a cause of loss form, and it tells us exactly which events, like fire, wind, or theft, are eligible for a payout.
Explaining Cause Of Loss Form to a small business owner
Your property policy has an attached form that spells out which disasters actually trigger coverage. We’ve placed you with the Special Causes of Loss Form, which is the broadest version available, but it still doesn’t cover everything, so let’s talk about what’s excluded, like flood, so there are no surprises later.
Explaining Cause Of Loss Form to a CFO or risk manager
The cause of loss form attached to your commercial property policy defines the peril scope, and we’ve confirmed Special form is in place across all locations for consistency. That said, Special form still excludes flood, earth movement, and a handful of other perils, so I’d like to walk through your exposure schedule to confirm whether standalone flood or earthquake coverage makes sense given your portfolio.
Frequently Asked Questions About Cause Of Loss Form
What is the difference between Basic, Broad, and Special causes of loss forms?
Basic form covers a short, specific list of perils like fire and lightning. Broad form adds more perils, including weight of ice and snow and certain water damage. Special form covers all direct physical loss unless specifically excluded, making it the broadest of the three.
Does the Special Causes of Loss Form cover everything?
No, Special form does not cover everything. It still excludes perils like flood, earth movement, war, and nuclear hazard, along with several other standard exclusions, so separate policies or endorsements are often needed for full protection.
Can a cause of loss form be changed at renewal without the client knowing?
A cause of loss form can be changed at renewal if the carrier or agency modifies the endorsement without flagging it clearly to the client. This is why comparing the actual attached form number, not just the policy’s marketing description, is essential during every renewal review.
Is a Businessowners Policy affected by cause of loss forms?
A Businessowners Policy typically incorporates causes of loss language directly into its coverage form rather than attaching a separate ISO cause of loss endorsement, but the underlying peril logic, Basic, Broad, or Special-equivalent, still applies. Agencies should confirm the specific BOP edition’s peril scope with the carrier’s manual.
What happens if a loss isn’t listed in the attached cause of loss form?
A loss that isn’t listed in the attached cause of loss form, and isn’t covered under an open-perils structure minus exclusions, results in a denied claim. This is exactly what happened in the snow load roof collapse example, where a Basic form left the peril uncovered.
Do all commercial property policies use ISO cause of loss forms?
Not all commercial property policies use ISO’s exact cause of loss forms. Many carriers file proprietary forms with similar structures and naming conventions, so agencies should always verify the actual peril language in the specific carrier’s form rather than assuming ISO standard forms apply.
Related Insurance Terms
- Named Peril Policy: A policy structure that only covers losses specifically listed in the policy, the same logic underlying the Basic and Broad Causes of Loss Forms.
- All-Risk Policy: An older industry term for open-perils coverage, now more accurately called open perils, which the Special Causes of Loss Form is designed to create.
- Open Perils Coverage: Coverage that applies to all causes of loss except those specifically excluded, the structural approach used by the Special Causes of Loss Form.
- Building and Personal Property Coverage Form: The base ISO commercial property form (CP 00 10) that requires an attached cause of loss form to define which perils actually trigger a claim.
- Exclusion: Specific perils or circumstances a policy does not cover, which remain critical to review even under the broadest Special Causes of Loss Form.
- Endorsement: A policy modification attached to a base form, the general category that cause of loss forms fall under within ISO’s commercial property program.
Sources and References
About the Author
Justin Goodman, CIC, CCIP, CISC, CLCS, CRIS, PCIA, QCLS, MFHR CEO and Co-Founder, Total CSR, Inc.
Justin Goodman is a third-generation insurance broker with over two decades in agency operations. He has trained more than 50,000 CSRs, account managers, and producers in commercial and personal lines coverage, from workers’ compensation to construction risk. He was named 2024 Insurance Journal Agent of the Year and one of the nation’s top five construction insurance experts by Risk & Insurance. He is the author of Retain, which applies cognitive science research on memory and knowledge transfer to insurance training, and speaks nationally on how agencies build durable technical expertise in their teams.