The Co-insurance Clause is a fundamental concept in commercial property insurance, testing the broker's Critical and Analytical Thinking. Its purpose is to ensure that the insured carries an amount of insurance that is a fair reflection of the property's total value (usually 80%, 90%, or 100%).

If the insured chooses to underinsure their property to save on premium, the co-insurance clause acts as a penalty mechanism during a partial loss. The insurer will only pay a portion of the loss based on the ratio of "what was carried" versus "what should have been carried." Consequently, the most common affect of this clause is that it may decrease the amount paid by the insurer (Option C), leaving the insured to pay the remainder out-of-pocket as a "co-insurer."

The RIBO Level 1 Blueprint requires brokers to perform the "Did/Should" calculation to illustrate this risk to clients during Consulting and Advising. A broker who fails to explain co-insurance risk is at high risk for an Errors and Omissions (E & O) claim. By ensuring the client understands that the "limit" isn't the only factor in a settlement, the broker demonstrates the Professionalism and Integrity required to manage complex commercial accounts. This clause encourages "insurance to value," which maintains the stability of the insurance pool. Identifying and explaining this potential reduction in indemnity is a core requirement of the Risk Assessment and Classification competency, ensuring the client is aware of their financial exposure before a loss occurs.