I've not been asked. i call and have a certificate faxed to whom ever and done.

The customers always ask. most have a minimum level of coverage.Plus vehicle coverage if on their property.
I carry $2 mil/4 mil ag. that covers every job I've done.
'Completed work' coverage is the most missed option I see with guys around here. but thats what you pay for.

Now I know why their rates are less than mine.