Per-Occurrence Deductibles for Related Claims

Why the Unit of Deductible Matters

A single event can injure several people or damage several properties, producing multiple claims. Under a per-occurrence deductible, the deductible is applied to the combined covered loss from the event, not separately to every claim. That choice can materially change how much the insured reimburses and how much loss remains with the insurer.

The calculation has two distinct steps: first determine which claims belong to the same occurrence under the assumed policy wording, then apply one deductible to that occurrence’s total covered loss. A shared date or location alone does not necessarily make separate incidents one occurrence; the policy’s definition and the facts about the cause govern. The examples below state the grouping explicitly so the arithmetic does not depend on interpreting disputed wording.

Definition: Suppose a policy has a per-occurrence deductible $D$. Let $X_{ij}$ be the covered loss for claim $j$ arising from occurrence $i$, measured before this deductible. The occurrence loss is $S_i=\sum_j X_{ij}$. With no policy limit or other adjustment in the calculation, the insured’s deductible responsibility for that occurrence is $R_i=\min(S_i,D)$, and the insurer’s net indemnity loss is $N_i=S_i-R_i=\max(S_i-D,0)$. If the insurer makes gross claim payments and then collects reimbursement from the insured, gross payments are $S_i$ and reimbursement is $R_i$; the insurer’s net loss is still $N_i$.

This formulation assumes the stated claims are covered, the deductible is a fixed dollar amount per occurrence, and no limit, coinsurance, expense treatment, or other provision changes the amounts. If policy wording imposes a limit or treats an item differently, the order and amount of payment must follow that wording; the simple equations should not be applied without adjustment.

Calculate Within Each Occurrence

The deductible does not reduce each claim independently. Add the covered claims assigned to an occurrence, compare that total with $D$, and calculate the reimbursement and net loss for that occurrence. If the occurrence total is below $D$, the insured is responsible for the whole total and the insurer’s net indemnity loss is zero. If the total exceeds $D$, the insured’s responsibility is capped at $D$, and the insurer bears the excess.

S_i=\sum_j X_{ij}, \qquad R_i=\min(S_i,D), \qquad N_i=\max(S_i-D,0).

For multiple occurrences, apply this calculation separately to each occurrence and then sum the results. The deductible is not automatically one annual deductible: a policy with a per-occurrence deductible generally applies a new deductible to each occurrence, subject to its terms.

Worked Example: Three Claims From One Occurrence

A hypothetical commercial policy has a $50,000 per-occurrence deductible. A single covered equipment failure causes three separate property claims of $18,000, $29,000, and $41,000. Assume the policy treats all three claims as one occurrence, with no limit or other adjustment. Calculate gross payments, the insured’s reimbursement, and the insurer’s net loss.

Method. Aggregate the related claims first, then apply one deductible to their occurrence total.

Step 1: Find the occurrence loss. The claims total $S=18{,}000+29{,}000+41{,}000=88{,}000$. The addition is $18,000 + $29,000 = $47,000, and $47,000 + $41,000 = $88,000.

Step 2: Find the reimbursement. Since $S>D$, reimbursement is $R=\min(88{,}000,50{,}000)=\$50{,}000$.

Step 3: Find the insurer’s net loss. The insurer’s net loss is $N=88{,}000-50{,}000=\$38{,}000$. If the insurer makes gross payments, those payments total $88,000 and the $50,000 reimbursement reduces its net loss to $38,000.

Check. Gross payments equal reimbursement plus net loss: $\$50{,}000+\$38{,}000=\$88{,}000$. The calculation avoids the common mistake of applying the $50,000 deductible to each claim separately.

Why the Formula Holds

The deductible allocates the first $D$ dollars of covered loss from each occurrence to the insured, but the insured cannot be responsible for more covered loss than the occurrence actually produced. These two conditions determine the reimbursement.

If $S_i\leq D$.
The occurrence has no loss above the deductible. The insured is responsible for all $S_i$, so $R_i=S_i$ and $N_i=S_i-S_i=0$.

If $S_i>D$.
The insured is responsible for the first $D$ dollars. The insurer bears the remaining $S_i-D$, so $R_i=D$ and $N_i=S_i-D$.

Together, the cases give $R_i=\min(S_i,D)$ and $N_i=\max(S_i-D,0)$. They also show why the two amounts reconcile: in either case, $R_i+N_i=S_i$. This identity is a useful check on every calculation.

Worked Example: One Occurrence Below the Deductible

A hypothetical property policy has a $40,000 per-occurrence deductible. One covered water-main rupture produces three claims of $12,000, $16,000, and $9,000. The policy treats the claims as one occurrence; assume there are no limits or other adjustments. Determine the reimbursement and insurer net loss.

Method. Combine the claims before comparing the total with the deductible.

Step 1: Total the claims. $S=12{,}000+16{,}000+9{,}000=37{,}000$, because $12,000 + $16,000 = $28,000 and $28,000 + $9,000 = $37,000.

Step 2: Calculate reimbursement. $R=\min(37{,}000,40{,}000)=\$37{,}000$. The total is below the deductible, so the insured is responsible for all covered loss in this occurrence.

Step 3: Calculate net loss. $N=37{,}000-37{,}000=\$0$. The insurer may have paid $37,000 gross if it administers the claims, but full reimbursement leaves zero net indemnity loss under these assumptions.

Check. Reimbursement plus net loss is $37,000 + $0 = $37,000, equal to gross payments. It would be wrong to charge three separate $40,000 deductibles: there is one occurrence, and its total loss is less than one deductible.

Separate Occurrences, Separate Applications

Claims from different occurrences are not combined merely because they happen during the same policy period. For each occurrence, total its covered claims and apply the deductible once. Only after calculating each occurrence’s reimbursement and net loss should the amounts be added across occurrences.

Worked Example: Two Occurrences in One Policy Period

A hypothetical policy has a $30,000 per-occurrence deductible. During the policy period, a covered loading-dock collision produces two claims of $23,000 and $17,000. A separate covered burst pipe produces claims of $52,000 and $14,000. Assume the policy treats each incident as one occurrence, and the two incidents as separate occurrences. There are no limits or other adjustments. Find total gross payments, total reimbursement, and insurer net loss.

Method. Calculate the deductible allocation separately for each occurrence.

Step 1: Loading-dock collision. Its occurrence total is $S_1=23{,}000+17{,}000=\$40{,}000$. Reimbursement is $R_1=\min(40{,}000,30{,}000)=\$30{,}000$. Net loss is $N_1=40{,}000-30{,}000=\$10{,}000$.

Step 2: Burst pipe. Its occurrence total is $S_2=52{,}000+14{,}000=\$66{,}000$. Reimbursement is $R_2=\min(66{,}000,30{,}000)=\$30{,}000$. Net loss is $N_2=66{,}000-30{,}000=\$36{,}000$.

Step 3: Add the occurrence results. Gross payments are $40{,}000+66{,}000=\$106{,}000$. Total reimbursement is $30{,}000+30{,}000=\$60{,}000$. The insurer’s net loss is $10{,}000+36{,}000=\$46{,}000$.

Check. Total reimbursement plus net loss is $60,000 + $46,000 = $106,000, equal to gross payments. Applying only one $30,000 deductible to the entire policy-period total would give a net loss of $106,000 - $30,000 = $76,000, which does not follow the stated per-occurrence structure.

Common Errors and a Practical Check

The main calculation trap is applying the deductible at the wrong level. A per-claim structure applies a deductible to each claim; a per-occurrence structure applies it once to the total loss from each occurrence. Neither should be confused with a single deductible applied to all losses in a policy period.

Wrong: deduct claim by claim. In the first example, this would produce reimbursements of $18,000, $29,000, and $41,000, totaling $88,000, and an insurer net loss of zero. Correct: the three claims form one occurrence, so reimbursement is $50,000 and net loss is $38,000.
Wrong: apply one deductible to the policy-period total. In the two-occurrence example, this would give $76,000 net loss. Correct: two distinct occurrences each receive their own $30,000 application, giving $46,000 net loss.
Wrong: reimburse more than the occurrence loss. When $S_i<D$, reimbursement is $S_i$, not $D$. The insured cannot reimburse a deductible amount greater than the covered loss used in the calculation.
Wrong: decide grouping from the claim count or date alone. Claim count does not determine the number of deductibles, and claims on the same date are not necessarily one occurrence. Use the assumed or actual policy definition of occurrence.

A reliable workflow is to label each occurrence, list its covered claims, total those claims, apply one deductible to that total, and reconcile gross payments as reimbursement plus insurer net loss. State the occurrence grouping as an assumption whenever it is supplied by the problem; do not silently infer it from timing alone. Correct aggregation is central to pricing and administering large deductible programs and is aligned with the CAS Exam 8 (Advanced Ratemaking) syllabus.

Check Your Understanding

For each problem, use the stated occurrence grouping and assume no policy limits or other adjustments unless specified.

A hypothetical policy has a $25,000 per-occurrence deductible. One covered machine fire, treated as a single occurrence, causes claims of $8,000, $11,000, and $9,000. Find the reimbursement and insurer net loss. (Answer: total loss $28,000; reimbursement $25,000; net loss $3,000.)
A hypothetical policy has a $40,000 per-occurrence deductible. One covered event produces claims of $14,000 and $19,000. Calculate gross payments, reimbursement, and net loss. (Answer: gross payments $33,000; reimbursement $33,000; net loss $0.)
A hypothetical policy has a $30,000 per-occurrence deductible. Occurrence A produces claims of $35,000 and $20,000; separate occurrence B produces claims of $12,000 and $18,000. Find total reimbursement and insurer net loss. (Answer: total reimbursement $60,000; net loss $25,000.)
A hypothetical policy has a $50,000 per-occurrence deductible. Three claims of $26,000, $31,000, and $18,000 arise from one occurrence. Calculate the correct insurer net loss, then calculate the net loss if someone incorrectly applied the deductible separately to each claim. (Answer: correct net loss $25,000; incorrect per-claim result $0.)
A hypothetical policy has a $35,000 per-occurrence deductible. Two claims of $44,000 and $16,000 arise from separate occurrences, even though they happen on the same date. Find total reimbursement and net loss. (Answer: reimbursement $51,000; net loss $9,000.)

What You'll Learn