Required from whom to whom and attached to what? Some perspective is always helpful. Are you asking about this:

"Do not file Form 1098-C for a contribution of a qualified vehicle with a claimed value of $500 or less. However, you may use it as the contemporaneous written acknowledgment under section 170(f)(8) by providing the donor with Copy C only. If you use Copy C as the acknowledgment, you must check box 7. In addition, do not complete boxes 4a through 5c or enter the donor's TIN on the form. You may, but are not required to, enter the donee's federal TIN on the form."