Final answer:
The deductible of a commercial liability umbrella policy is called the SIR (Self-Insured Retention).
Step-by-step explanation:
The deductible of a commercial liability umbrella policy is called the SIR (Self-Insured Retention). It is the amount that the insured party must pay out of pocket before the insurance coverage kicks in. The purpose of the SIR is to prevent smaller claims from being filed and reduce administrative costs for the insurance company.