WHY DO YOU CHARGE FARMERS SALES TAX ON OIL & GREASE?

Farmers are exempt from sales tax on ag diesel but we must charge sales tax on oil and grease and other supplies that farmers purchase. The Iowa Department of Revenue makes this clear. Here is what they say:

http://www.iowa.gov/tax/educate/faqsales.html#9  (see question # 9, section on 'parts and supplies')

Do farmers pay sales tax on the purchases they make?

Parts and supplies

"Replacement parts used in the operation of eligible farm machinery or equipment are exempt from sales tax. Oil filters, spark plugs, gas filters, and tires are examples of exempt replacement parts. Do not confuse replacement parts with supplies, most of which are taxable. Oil and grease used in the routine maintenance of a tractor, for example, are not considered parts; they are considered supplies. They are taxable".