State or federal?
And while you are granted one deferrment "as of right" (up to ~6 months I believe), after that, you can try calling the clerk to explain your excuse, but most often, they require you to come in and argue in person on the date on the summons.
If it's any consolation, there's no lawyer on the planet who would select you to be on a jury if, at the start of their questions to you, you tell them that your business will "go under" if you're put on the jury. (No lawyer wants a juror who's angry at them deciding their client's fate!)