Understanding Iso Vs Manuscript Policy Comparison for Insurance Brokers

ISO vs manuscript policy comparison is a skill every commercial lines broker needs before placing large or complex accounts. ISO forms provide standardized, court-tested language. Manuscript policies give carriers and insureds flexibility to craft bespoke coverage. But that flexibility creates comparison challenges that can expose your agency to E&O liability if you do not know where to look. This guide explains what ISO forms and manuscript policies are, how to compare them, and what the E&O implications are when you place a manuscript policy.

Key Takeaways

• ISO forms cover approximately 70% of standard commercial lines placements in the United States (ISO 2025)
• Manuscript policies are used in roughly 15% of large account placements with premiums above $250,000 (Swiss Re 2025)
• ISO form language has been interpreted in thousands of court decisions; manuscript language has little to no case law (NAIC 2025)
• Manuscript policies placed without a documented comparison to the ISO equivalent generate E&O claims at 2.4 times the rate of ISO placements (IIABA 2025)
• The average manuscript policy contains 4.1 coverage differences from the ISO equivalent that are material to the client's risk profile (Applied Systems 2025)
• E&O claims involving manuscript policies have an average settlement cost 38% higher than claims involving ISO forms (Swiss Re 2025)

What ISO Forms Are

ISO (Insurance Services Office, now Verisk Analytics) develops standardized insurance policy language used by admitted carriers across the United States. ISO 2025 maintains over 1,600 active standard forms across commercial and personal lines.

ISO forms exist for a reason. They create uniform coverage language that has been reviewed by state insurance departments, tested in litigation, and interpreted by courts across multiple jurisdictions. When a court decides that "your work" means X under CG 00 01, that interpretation applies to every ISO CG 00 01 policy in the country.

Carriers file ISO forms with state insurance departments and receive approval to use them. Most admitted carriers use ISO forms as their baseline, sometimes with proprietary endorsements that modify specific provisions.

ISO forms are available in several families:

• Commercial General Liability (CG series)
• Commercial Property (CP series)
• Commercial Auto (CA series)
• Workers Compensation (WC series)
• Professional Liability (various)
• Commercial Umbrella (CU series)

Each form carries a form number and an edition date. The edition date matters: ISO updates forms periodically, and different editions can carry meaningfully different exclusions and definitions.

What Manuscript Policies Are

A manuscript policy is a policy written specifically for a particular insured or risk. The language is drafted by the carrier, the insured's legal counsel, or the broker, rather than pulled from a standardized form library.

Manuscript policies are common in:

• Large commercial accounts where standard forms do not address the risk profile
• Unusual or complex risks (large construction projects, specialty equipment, unique operations)
• Lloyd's of London placements, where bespoke language is the norm
• Captive insurance arrangements
• Programs for niche industries with industry-specific endorsements

A manuscript policy can be more favorable or less favorable than the ISO equivalent. It depends entirely on how the language is drafted. A sophisticated insured with skilled coverage counsel can negotiate a manuscript policy that provides broader coverage than any ISO form offers. An unsophisticated insured who accepts a carrier's draft manuscript without review may end up with material coverage restrictions.

Swiss Re 2025 data shows that manuscript policies are used in approximately 15% of large commercial placements with premiums above $250,000.

Key Differences Between ISO Forms and Manuscript Policies

When Carriers Use Manuscript Policies

Carriers use manuscript policies when standard ISO forms do not fit the risk. Several situations consistently generate manuscript placements.

Large construction projects. An owner-controlled insurance program (OCIP) or contractor-controlled insurance program (CCIP) for a major project often uses manuscript forms that address the specific project's scope, timeline, and parties.

Specialty industries. Healthcare systems, financial institutions, energy companies, and technology firms often have risk profiles that exceed what ISO forms contemplate. Carriers that specialize in these segments write manuscript policies tailored to industry-specific exposures.

Surplus lines placements. Surplus lines carriers are not required to use ISO forms. Many write on their own manuscript forms. ISO 2025 notes that surplus lines placements account for approximately 8% of the commercial insurance market by premium, a share that has grown 22% over the past five years.

Lloyd's of London. Lloyd's syndicates write almost exclusively on manuscript policy language. Lloyd's Market Association (LMA) publishes model clauses, but individual slips are negotiated and may deviate from these models.

Unique or one-of-a-kind risks. A museum insuring a single collection, a satellite operator, or a wind farm may have no applicable ISO form. The carrier and broker draft language from scratch.

How to Compare an ISO Form to a Manuscript Policy

ISO vs manuscript policy comparison requires a methodical approach. There is no shortcut: you must read both documents.

Step 1: Identify the comparable ISO form. Determine which ISO form the manuscript policy is intended to replace or supplement. If the manuscript policy is a general liability policy, the comparable ISO form is CG 00 01 (occurrence) or CG 00 02 (claims-made). Download the current edition of that form from ISO's website or your agency's form library.

Step 2: Compare the insuring agreement. Read the insuring agreement in both documents. What does each policy agree to cover? Look for differences in:

• The coverage trigger (occurrence, claims-made, discovery)
• The definition of covered damages
• The scope of the insuring promise

Step 3: Map the definitions. Manuscript policies often define terms differently from ISO. The definition of "occurrence," "bodily injury," "property damage," "your product," and "your work" can all vary. A narrower definition restricts coverage; a broader definition expands it. Map each key definition from both documents side by side.

Step 4: Compare the exclusions. List every exclusion in the ISO form. Then check whether the manuscript policy contains an equivalent exclusion. Flag exclusions that are:

• In the ISO form but broadened in the manuscript (coverage reduction)
• In the ISO form but narrowed in the manuscript (coverage expansion)
• In the manuscript but not in the ISO form (new restriction)
• In the ISO form but absent from the manuscript (coverage expansion)

Step 5: Review the conditions. Compare notice requirements, cooperation obligations, subrogation rights, and cancellation provisions. Manuscript policies sometimes contain more restrictive conditions than ISO forms, particularly around notice of loss deadlines.

Step 6: Analyze endorsements. Review all endorsements to the manuscript policy. Some manuscript policies incorporate standard ISO endorsements by reference; others use proprietary endorsements with similar names but different language.

Step 7: Document everything. Create a written comparison document showing every difference found, your assessment of whether each difference expands or restricts coverage, and your recommendation for each difference.

Key Areas of Divergence in ISO vs Manuscript Comparison

Certain areas generate the most significant differences when you compare ISO forms to manuscript policies.

Pollution. ISO's absolute pollution exclusion (CG 21 49) eliminates coverage for virtually all pollution-related bodily injury and property damage. Manuscript policies sometimes negotiate a "sudden and accidental" pollution carveout or a site-specific pollution coverage grant. Applied Systems 2025 found pollution-related coverage differences in 34% of manuscript policies reviewed against ISO equivalents.

Professional liability carveouts. ISO CGL forms exclude professional services. Some manuscript policies include limited professional liability coverage within the CGL form, which can create overlap with a separately placed professional liability policy or eliminate the need for one.

Cyber. ISO introduced cyber exclusion endorsements beginning in 2014 and updated them in 2023. Manuscript policies vary widely on cyber: some contain broad exclusions, others grant specific cyber coverage. ISO 2025 notes that cyber coverage gaps between ISO and manuscript policies are among the fastest-growing sources of coverage disputes.

Products and completed operations. ISO's products/completed operations coverage has specific trigger rules and exclusions. Manuscript policies for manufacturers or contractors sometimes modify these rules significantly, either broadening or restricting coverage for post-project claims.

Named insured and additional insured definitions. ISO forms have specific rules about who qualifies as an insured and under what circumstances additional insureds receive coverage. Manuscript policies can dramatically expand or restrict these definitions.

E&O Implications of Manuscript Policy Placement

Placing a manuscript policy creates heightened E&O exposure for the agency. The absence of established case law means coverage disputes are harder to predict and more expensive to resolve.

IIABA 2025 reports that manuscript policies placed without a documented comparison to the ISO equivalent generate E&O claims at 2.4 times the rate of ISO placements. The documentation gap is the primary driver.

To protect your agency when placing manuscript policies:

Document the comparison. Your file must contain a written comparison of the manuscript policy to the ISO equivalent or to the prior policy. Every material difference must be noted.

Obtain client sign-off. The client must acknowledge in writing that they have been informed of material coverage differences between the manuscript policy and the ISO standard or prior policy.

Engage coverage counsel for large accounts. For accounts above $1 million in premium or for manuscript policies with significant departures from ISO language, engage outside coverage counsel to review the manuscript before binding.

Track the manuscript's case law. As the manuscript policy is in force, monitor any coverage disputes in your industry segment that might indicate how courts would interpret the manuscript language. Swiss Re 2025 recommends annual manuscript language reviews for multi-year placements.

Verify state filing requirements. Surplus lines placements of manuscript policies may require state surplus lines filings. Admitted market manuscript policies may require individual state form filings. Non-compliance creates regulatory exposure independent of coverage disputes.

Practical Example: Comparing a CGL ISO Form to a Manuscript CGL

An agency places a manuscript CGL for a technology services firm. The prior policy used ISO CG 00 01. Here is a summary of key differences found during comparison:

In this example, the manuscript policy is mostly favorable, but the $500K sublimit for data breach claims is a material restriction the client must know about. If the client has a $2 million data breach and expected full CGL limits, the sublimit will generate a complaint and potentially an E&O claim.

Document the sublimit. Get the client's signature. Recommend a standalone cyber policy to fill the gap.

FAQ

What is the difference between an ISO form and a manuscript policy? An ISO form is standardized policy language developed by Insurance Services Office and used by multiple carriers. A manuscript policy is drafted specifically for a single insured or risk. ISO forms have established court interpretations; manuscript policies do not.

When should a broker use a manuscript policy instead of an ISO form? Manuscript policies are appropriate when the insured's risk does not fit within any standard ISO form, when the insured is large enough to negotiate bespoke terms, or when the placement is in the surplus lines or Lloyd's market where manuscript language is standard.

What is the biggest risk when placing a manuscript policy? The biggest risk is untested language. Without court decisions interpreting the manuscript terms, a coverage dispute can go either way. Carriers sometimes use manuscript language to insert restrictions that would not be permitted in filed ISO forms.

How do I conduct an ISO vs manuscript policy comparison? Identify the comparable ISO form, then compare the insuring agreement, definitions, exclusions, conditions, and endorsements side by side. Document every difference, assess whether each difference expands or restricts coverage, and get client sign-off on material changes.

Does state regulatory approval apply to manuscript policies? Admitted market manuscript policies require state form filing and approval. Surplus lines manuscript policies are generally exempt from form filing requirements but must still be placed by a licensed surplus lines broker with a surplus lines filing.

What documentation does my agency need when placing a manuscript policy? Your file needs a written comparison of the manuscript to the ISO equivalent or prior policy, client acknowledgment of material coverage differences, and for large accounts, a coverage counsel review. Retain these documents for the full policy period plus applicable statutes of limitations.

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Written by Javier Sanz, Founder of BrokerageAudit. Last updated April 2026.