What it means
The base is a starting amount for a reinsurance calculation. An agreed percentage can be applied to the defined subject premium to determine a charge, and the result is neither total revenue nor accounting profit.
Written premium differs from earned premium, since written premium relates to insurance business written during the relevant period while earned premium recognises coverage provided over time, and replacing one with the other can change the calculation substantially. The Casualty Actuarial Society's reinsurance-pricing material distinguishes GNWPI for risks-attaching policies from gross net earned premium income for losses-occurring policies.
The distinction concerns which business and period the treaty covers, and it should not be reduced to two interchangeable names for premium revenue. The coverage period matters as much as the total, because a risks-attaching treaty can cover policies that begin during a defined period even when losses arise later, so the relevant written-premium records must match that scope.
The word gross refers to the treaty being priced, whose own reinsurance premium is not deducted from the base in a way that makes the calculation circular. The word net can refer to other reinsurance that inures to the benefit of that treaty.
Inuring reinsurance provides protection that is considered before the treaty under review, so a surplus-share arrangement may remove part of the underlying exposure before a per-risk treaty responds, and the premium base should reflect the adjustments the parties agreed for that protection. Cancellations, refunds and other adjustments also depend on the wording, so a summary should not assume that every contract deducts the same items in the same order.
Read the definition and supporting schedules before applying the stated rate. A treaty can use provisional or adjustable premiums, with the insurer paying an initial amount and later reporting actual subject premium for reconciliation, and minimum or deposit provisions can change the final payment, so multiplying a rate by GNWPI may be only one step.
Accuracy requires consistent data. Premium records should identify the covered business, dates and adjustments, with reconciliations to source systems, because a correct percentage applied to an incomplete base still produces an incorrect result.
Changes in the book of business can also affect interpretation, since a larger GNWPI might reflect more policies, higher prices or different risks rather than a proportional increase in the reinsurer's expected losses. For managers, the concept explains why a reinsurance invoice may not match a familiar premium total.
Ask for a bridge from gross written premium to the agreed subject base, then from that base to the amount owed, which separates data issues from disagreements about the rate. Reports should retain the exact contractual definition, stating the business included, deductions applied, period and rate and distinguishing provisional from final figures, and should avoid replacing the defined base with a similarly named accounting metric merely because it is easier to obtain.
In practice
Real-world examples.
Example
An insurer writes $12 million of covered business and deducts $2 million of premium associated with inuring reinsurance under the treaty definition. The resulting GNWPI is $10 million before the treaty's own charge.
Example
A finance team substitutes earned premium for written premium in an invoice calculation. The reviewer identifies the mismatch because the contract covers risks attaching during the treaty year.
Example
A reinsurance agreement includes a minimum premium. The accountant checks that provision after calculating the rate-based amount rather than assuming multiplication alone determines the final payment.
Formula
Calculation
Illustrative rate-based reinsurance premium = defined GNWPI x agreed rate. A $10 million base at 2% produces $200,000 before any further contractual adjustment.
If the agreement requires a $220,000 minimum, the minimum may control despite the lower rate-based result. The example is not a universal formula for all reinsurance because definitions, minimums and adjustment terms differ.Case study
Seen in the real world.
Fictional case study: Harbor Insurance received a reinsurance invoice that exceeded its internal forecast. The forecast used an earned-premium figure and deducted the treaty premium itself from the calculation base. The reviewer rebuilt the bridge using the contract's written-premium scope and permitted inuring adjustments.
Finance then checked the minimum-premium condition separately. Harbor corrected the forecast and documented the base definition for future reconciliations. The team stopped treating the invoice difference as a rate error when the original problem was the premium base.
Watch out
Common mistakes.
- Treating GNWPI as ordinary net written premium. The treaty definition determines the specific adjustments.
- Substituting earned premium for written premium. Coverage timing and the agreement's basis matter.
- Ignoring minimum and adjustment provisions. The rate-based calculation may not be the final amount owed.
Questions
People also ask.
Why is the term both gross and net?
It can be net of other reinsurance benefiting the treaty but gross of the reinsurance being priced.
Is GNWPI the insurer's profit?
No. It is a defined premium base, not the amount left after claims, expenses and other costs.
What should finance reconcile?
Reconcile covered written premium, contractual deductions, the applied rate and any minimum or later adjustment to the final payment.
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