Requiring a subcontractor to provide a certificate of insurance BEFORE it starts work is a best practice primarily because it:

Giải thích

Checking the certificate before the sub mobilizes verifies that the required coverage exists at the moment exposure begins, when it is still possible to keep an uninsured sub off the site. (a) confuses receiving a document with buying a policy. (b) reads the certificate as controlling the insurer, which it does not — cancellation rights live in the policy. (c) reverses the transfer: the purpose is to reach the sub's insurer for the sub's work, not to spend the general contractor's own limits on it.