If this is a single member LLC and you were "open for business" on or before Dec 31 of the tax year, then you are required to file a SCH C with your personal 1040 tax return. It doesn't matter if the business reports $0 income either.
Otherwise, if you were not "open for business" on or before Dec 31 of the tax year, you have absolutely nothing to report on SCH C and do not need to complete one.
