Anti-Concurrent Causation Clause
Also known as: ACC Clause, Anti-Concurrent Causation Language, ACC
An anti-concurrent causation clause is a lead-in provision, usually attached to a group of property exclusions, stating that the insurer will not pay for loss caused directly or indirectly by an excluded peril, whether or not any other cause or event contributes concurrently or in any sequence. In plain terms, if an excluded peril is part of the causal chain at all, the entire loss is excluded — even if a covered peril was the main driver. It exists specifically to reverse the policyholder-friendly result that the concurrent causation doctrine would otherwise produce.
For a small-business buyer, an ACC clause can dramatically shrink what a property policy actually pays after a mixed-cause catastrophe. The most common battleground is storm damage: if wind (often covered) and flood (typically excluded) both damage a building, an ACC clause can allow the insurer to deny the full loss because the excluded flood contributed. This is why relying on a standard property form for catastrophe exposure is risky, and why standalone flood or earthquake policies are often essential rather than optional.
The important nuance is that ACC clauses are not enforced uniformly. Some states uphold them as written, giving exclusions sweeping effect; others hold that a mandatory efficient-proximate-cause rule overrides the clause, so a covered predominant cause still triggers coverage. The specific wording and its placement relative to the exclusions also affect enforceability. Buyers should ask their broker whether their form contains ACC language, understand how their state treats it, and fill the resulting gaps with dedicated flood, earthquake, or difference-in-conditions coverage before a loss occurs.
Real-world scenario
Gulf Breeze Seafood Grill, a waterfront restaurant on the Florida panhandle, insured its building for $1,200,000 and its kitchen equipment and contents for $350,000 under a commercial property policy costing $18,400 a year. The special-form policy carried a 5% named-storm deductible — $60,000 on the building — and, buried in the water-damage exclusion, an anti-concurrent causation (ACC) clause reading that the insurer would not pay for loss caused \"directly or indirectly\" by flood, \"regardless of any other cause or event contributing concurrently or in any sequence.\"
When a Category 2 hurricane made landfall, wind tore off part of the roof while a 4-foot storm surge flooded the dining room. Adjusters put the total physical damage at $540,000 — roughly $180,000 traceable to wind and $360,000 to the surge. Under a pure concurrent causation reading, the owner expected the full wind share to be paid. Instead, the ACC clause let the carrier deny every dollar of loss where wind and water combined: the property policy paid only the $120,000 of clearly dry, wind-only roof damage — $60,000 net after the deductible — and denied the remaining $420,000, including $60,000 of wind damage inside the flooded dining room.
Because Gulf Breeze had separately bought a flood policy with a $500,000 building limit, it recovered $360,000 for the surge. But the $60,000 of ACC-denied wind damage in the dining room fell into a gap — denied by the property carrier and outside the flood policy because it was not flood damage. Add the $60,000 deductible, $95,000 of lost business income and $28,000 of extra expense during the 11-week closure (also barred because the shutdown stemmed from flood), and $42,000 in attorney fees fighting the denial, and the owner absorbed roughly $285,000. A standalone difference-in-conditions layer costing about $9,500 a year would have closed most of that gap.
How it affects your premium
An anti-concurrent causation clause is contract language, not a coverage you buy — so it has no standalone "premium." What it changes is how much of a mixed-peril loss your existing property premium actually protects, and these factors drive the exposure it creates:
- Catastrophe exposure of the location: Coastal, floodplain, and seismic addresses are where ACC clauses bite hardest, because wind, water, and earth movement routinely combine in one event.
- Breadth of the water and earth-movement exclusions: The wider the excluded perils the ACC language attaches to, the more of a combined loss the carrier can deny.
- Named-storm and wind/hail deductible structure: A high percentage deductible stacks on top of an ACC denial, enlarging the uninsured slice.
- Whether separate flood or quake coverage exists: Standalone flood or earthquake policies backfill the excluded peril the ACC clause carves out.
- Policy form and jurisdiction: Some states enforce ACC language strictly while others favor efficient-proximate-cause rules, changing the real-world outcome.
- Presence of a difference-in-conditions layer: A DIC buy-back can override the gap the clause creates for a modest added premium.
Common misconceptions
Myth: If wind (a covered peril) plays any part in the damage, my property policy has to pay for that portion.
Reality:
Not when an anti-concurrent causation clause applies. The clause is specifically written to bar the entire loss whenever an excluded peril like flood contributes "concurrently or in any sequence," which is the opposite of a pure concurrent causation result.
Myth: Anti-concurrent causation language only shows up in flood claims.
Reality:
It appears anywhere covered and excluded perils can combine — hurricane wind-plus-surge, earthquake-plus-fire, or mudslide-plus-rain. A difference-in-conditions policy is often the cleanest way to buy back the gap it creates.
Myth: A broad special-form ('all-risk') policy makes ACC language irrelevant.
Reality:
Special form covers many perils but still excludes flood and earth movement, and the ACC clause attaches to those exclusions — so an open-perils policy can still deny a combined loss.
Frequently asked questions
What is an anti-concurrent causation clause in plain English?
It is policy wording that says if a loss is caused by both a covered peril and an excluded peril acting together or in sequence, the insurer pays nothing for that loss — even for the part the covered peril caused on its own.
How is it different from concurrent causation?
Under concurrent causation, a loss with any covered cause can trigger coverage; the anti-concurrent clause reverses that by using the excluded peril to defeat the whole claim.
How do I protect my business against this gap?
Buy the excluded peril back separately — a standalone flood policy or earthquake coverage — or add a difference-in-conditions layer so the combined loss is covered somewhere.
Does the clause apply to hurricane wind versus storm surge?
Yes. Storm surge is treated as flood, so where wind and surge both damage a building the ACC clause can bar the claim. Understanding flood vs. storm surge matters for how the loss is split and paid.
Where do I find this clause in my policy?
Look in the exclusions section of your causes of loss form, usually inside the water-damage or earth-movement exclusion, for phrases like 'regardless of any other cause or event contributing concurrently or in any sequence.'
Sources cited
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