What Is Concurrent Causation — and Why Does It Matter?

Concurrent causation is a concept that arises when two or more perils — one covered by your policy and one excluded — act together to produce a single, indivisible loss. Under the traditional concurrent causation doctrine, courts generally held that if a covered peril was part of the causal chain, the entire claim should be paid. This was considered the fair, policyholder-friendly standard.

For example, imagine floodwaters weaken a riverbank, causing a landslide that damages your parked vehicle. The landslide (an excluded peril) and the flood (also often excluded) combine to total your car. But what if a covered peril like wind or collision was also involved? That's where things get complicated — and that's exactly where the anti-concurrent causation clause enters the picture.

How the Anti-Concurrent Causation Clause Works to Deny Claims

The anti-concurrent causation (ACC) clause is a provision insurers include in policy exclusion sections to override the pro-policyholder concurrent causation doctrine. It states that a loss is excluded if an excluded peril contributed to the damage in any way, in any sequence, or at any time — even if a covered peril also played a role.

The language typically reads something like:

"We will not pay for loss or damage caused directly or indirectly by [excluded peril]. Such loss is excluded regardless of any other cause or event that contributes concurrently or in any sequence to the loss."

This is a sweeping clause. It doesn't require the excluded peril to be the primary cause — it only requires that the excluded peril be somewhere in the chain of events. The result: insurers can deny the entire claim, including the covered portion, without having to separate or apportion the two causes of damage.

As of May 2026, ACC clauses remain enforceable in most U.S. states, with no uniform federal prohibition. Their enforceability continues to vary significantly by jurisdiction. A January 2026 Illinois appellate court decision (Lido Hospitality, Inc. v. AIX Specialty Insurance Co.) reaffirmed that a clearly worded ACC clause can bar coverage for a collapse claim — signaling that courts in enforcement states continue to uphold the clause as written. Learn more about your rights when it comes to disputing claim denials and low offers if the ACC clause is used against you.

Real-World ACC Claim Denial Examples

Understanding the ACC clause in abstract terms is helpful, but seeing how it plays out in actual claim scenarios makes the risk much more concrete. If your claim has ever been denied, learning about common claim denial reasons and how to appeal can give you a solid starting point.

Example 1: Flood + Collision

You're driving during a flash flood and hydroplane off the road, striking a guardrail. Your vehicle sustains collision damage (a covered peril under your collision coverage) and flood damage (an excluded peril under most standard auto policies). When you file your claim, the insurer discovers that floodwater entered the engine compartment and contributed to the total loss.

Result with ACC clause: The insurer denies the entire claim — including the collision portion — because flood, an excluded peril, contributed to the loss "in any sequence." Florida's OIR issued a February 2025 informational memorandum reminding insurers to properly evaluate concurrent causation claims and required all authorized residential property insurers to submit detailed 2024 hurricane season data by March 6, 2025 — warning that improper ACC denials would result in regulatory action and consumer restitution. Learn more about hurricane and flood coverage for your car if you live in a storm-prone area.

Example 2: Earthquake + Vandalism

An earthquake causes a retaining wall to collapse onto your vehicle (excluded peril). During the chaos, vandals also break your windows and slash your tires (covered under comprehensive). You file a comprehensive claim for the vandalism.

Result with ACC clause: If your policy excludes earthquake damage and contains an ACC clause, the insurer may deny the vandalism portion entirely because the earthquake — an excluded peril — "contributed concurrently to the loss."

Example 3: Mechanical Breakdown + Collision

Your brakes fail (mechanical breakdown — often excluded), causing you to rear-end another vehicle. The collision caused the physical damage.

Result with ACC clause: In policies where mechanical or electrical failure is excluded and ACC language is present, the insurer may attempt to deny coverage by arguing that the excluded mechanical failure was a contributing concurrent cause. This is one of the most frequently cited exclusions in ACC-related auto claim disputes.

States That Limit or Prohibit ACC Clauses

Not all states allow insurers to use anti-concurrent causation clauses freely. Enforceability varies significantly depending on where you live. As of May 2026, no new states have enacted full prohibitions — the legislative landscape remains mostly unchanged, with pending bills in New York and New Jersey still stalled in committee. Legislative pressure continues to build in several jurisdictions, and regulatory scrutiny is intensifying even in states that currently enforce ACC clauses. This is one reason why understanding your state-specific car insurance protections is so important — especially if you live in a hurricane or flood-prone area.

In California and Washington, the efficient proximate cause doctrine is the controlling standard. Under this rule, courts look at which peril was the dominant or primary cause of the loss — and if that peril is covered, the claim must be paid regardless of secondary excluded causes. This makes ACC clauses largely unenforceable in those states. North Dakota and West Virginia similarly decline to enforce ACC clauses under their state doctrines.

In New York, Senate Bill S6205 — introduced in March 2025 and aimed at barring ACC denials in flood-combined losses — has not advanced beyond the Senate Insurance Committee as of May 2026. New Jersey's comparable Assembly Bill A1647 also remains unenacted. While both states continue to enforce ACC clauses as written, the legislative push signals growing momentum for reform.

Florida's OIR demanded detailed hurricane claim data from all authorized insurers by March 6, 2025 — specifically targeting concurrent causation denial patterns — and confirmed that market conduct exams reviewing 2024 storm claims are ongoing. Regulatory scrutiny is intensifying even in states that currently enforce ACC clauses.

How to Find ACC Language in Your Policy

ACC clauses are intentionally buried in the exclusions section of your policy. Here's how to locate them:

1. Open your policy's Declarations or Full Policy Document — usually available via your insurer's online portal or by request.
2. Navigate to the "Exclusions" or "Causes of Loss" section — this is where excluded perils are listed.
3. Search for these trigger phrases:
   • "concurrently"
   • "in any sequence"
   • "regardless of any other cause"
   • "directly or indirectly"
   • "whether or not combined with"
4. Look at the preamble to exclusions — many ACC clauses appear as a blanket statement that applies to all listed exclusions, not just one.

If you find language stating the exclusion applies "regardless of any other cause or event that contributes concurrently or in any sequence to the loss" — that is a classic ACC clause.

If you can't find this language, your policy may default to the pro-policyholder concurrent causation doctrine. However, you should confirm this interpretation with an insurance attorney or licensed public adjuster. You can also reference the car insurance damage assessment process to understand how insurers investigate and document individual causes of loss.

How to Dispute an ACC-Based Claim Denial

If your claim has been denied citing the anti-concurrent causation clause, you have options. The process requires persistence, documentation, and in many cases professional help. Understanding your rights when it comes to disputing your claim through the appraisal clause can also be a powerful tool in your arsenal.

Step 1: Request the Full Denial Letter

Demand a written denial letter that specifically cites the exact policy language used to deny your claim. Vague denials are harder for insurers to defend and may signal a weak legal foundation for the ACC invocation.

Step 2: Document Each Cause of Loss Separately

Hire an independent engineer, mechanic, or damage assessor to provide a written report attributing specific damage to specific causes. If flood caused engine damage but the collision caused frame damage, having that clearly separated gives you significant leverage. Consider filing a supplemental claim to document newly identified damage once causation is separated and established.

Step 3: Challenge ACC Enforceability in Your State

Review your state's rules. If you're in California, Washington, North Dakota, West Virginia, or another state with efficient proximate cause protections, cite those laws directly in your appeal. Reference the specific court precedents that make ACC clauses unenforceable in your jurisdiction.

Step 4: File a Formal Appeal with Your Insurer

Submit a written appeal with supporting documentation. Include:

• A clear timeline of events showing the sequence of causes
• Independent expert reports
• Your state's legal standard on concurrent causation
• The argument that the covered peril was the efficient proximate cause

Step 5: File a Complaint with Your State Insurance Department

If the insurer refuses to reconsider, file a formal complaint with your state's Department of Insurance. Regulators take bad-faith denial patterns seriously — Florida's OIR, for example, confirmed it will pursue market conduct exams and consumer restitution for improper concurrent causation denials. For context on full escalation options — including state DOI complaint processes and arbitration — review the car insurance dispute resolution process.

Step 6: Consult an Insurance Attorney or Public Adjuster

For large claim amounts, retaining a licensed public adjuster or bad-faith insurance attorney can make a significant difference. Attorneys who specialize in insurance disputes understand how to argue concurrent causation cases and can shift the burden of proof back to the insurer. You can also learn more about why insurance claim denials happen and how to fight back to strengthen your position.

Frequently Asked Questions

Does the anti-concurrent causation clause apply to all car insurance policies?

Not all auto insurance policies contain an ACC clause. It is more commonly found in homeowners and commercial property policies, but many standard personal auto policies include exclusion language that mirrors ACC intent — particularly for flood, earthquake, and mechanical breakdown exclusions. Always read your full policy exclusions section, not just the coverage summary. When in doubt, ask your agent to walk you through each exclusion and whether ACC language applies to it.

Can an insurer use the ACC clause to deny a collision claim if flooding also contributed?

Yes — in states where ACC clauses are enforceable, an insurer can deny a collision-related claim if floodwater also contributed to the vehicle's damage. The insurer does not need to prove flood was the primary cause, only that it contributed "in any sequence." This is why comprehensive coverage matters, and why understanding how hurricane and flood coverage works for cars is critical if you live in a flood-prone area.

What is the difference between the ACC clause and the efficient proximate cause doctrine?

The efficient proximate cause doctrine asks: what was the dominant cause of the loss? If that dominant cause is covered, the whole claim is covered. The ACC clause eliminates this analysis entirely — it says that if any excluded peril contributed to the loss, the whole claim is denied. States like California, Washington, North Dakota, and West Virginia apply the efficient proximate cause doctrine, which makes ACC clauses largely unenforceable there. The two approaches represent fundamentally different philosophies on who should bear the risk of mixed-cause losses.

How can I protect myself from an ACC clause denial before a loss happens?

The best protection is thorough coverage. Purchase comprehensive auto coverage that includes as many perils as possible, minimizing the chance that any contributing cause is excluded. Review your policy exclusions annually, ask your agent about ACC language specifically, and consider adding endorsements for flood or earthquake if you live in high-risk areas. Checking your hail damage car insurance coverage is another good example of the type of detailed policy review you should perform for each weather-related peril.

Is an ACC-based claim denial considered bad faith insurance?

In some states and under specific circumstances, yes. If an insurer applies an ACC clause to deny a clearly covered loss, or invokes the clause in a state where it is legally unenforceable, that conduct could rise to the level of bad faith insurance. Courts in several states have issued significant bad faith verdicts against insurers for improper claim denials. Filing a complaint with your state's Department of Insurance and consulting with an attorney experienced in car insurance settlement disputes and bad faith is the right course of action in those situations.