Kentucky Form 51A158, the Farm Exemption Certificate, is what you give a vendor to buy qualifying farm supplies, machinery, feed, seed, chemicals, and fuel without paying the state’s six-percent sales tax. It works as a blanket certificate: one completed form covers every future exempt purchase from that seller until you revoke it in writing. Before you can use it, though, you need a Kentucky Agriculture Exemption Number from the Department of Revenue.
Get Your Agriculture Exemption Number First
You cannot use Form 51A158 without a valid Agriculture Exemption Number. KRS 139.481 requires every person claiming a farm-related sales tax exemption to give this number to the seller at least once before making tax-free purchases.
Apply using Form 51A800 (Sales and Use Tax Application for Agriculture Exemption). You’ll need to attach documentation showing your farming operation is a real business, not a hobby. Any of the following works:
- IRS Schedule F (Profit or Loss from Farming)
- IRS Form 4835 (Farm Rental Income and Expenses)
- Your Farm Service Agency number, the USDA-assigned number for the land where the farming happens
- Other documentation that satisfies the Commissioner you qualify
Submit the application to the Kentucky Department of Revenue, Division of Sales and Use Tax by mail (PO Box 181, Station 66, Frankfort, KY 40602-0181), fax ((502) 564-2041), or email (DOR.WebResponseSalesTax@ky.gov). After approval, the Department mails you a letter with your number. The current round of numbers expires December 31, 2026, and every four years after that. If you stop farming before your number expires, you have sixty days to notify the Department.
Eligibility under KRS 139.481 is limited to people regularly engaged, as a business, in tilling and cultivating the soil for crop production; raising and feeding livestock whose products ordinarily constitute food for human consumption; raising and feeding poultry; producing milk for sale; or raising ratite birds, llamas, alpacas, buffalos, cervids, or aquatic organisms. Hobby farms, backyard gardens, and pets do not qualify.
How to Fill Out Form 51A158
Download the current version from the Kentucky Department of Revenue website (revenue.ky.gov). It’s a single page.
At the top, print your legal name, farm location, and mailing address. Enter your driver’s license number and issuing state, and enter your Kentucky Agriculture Exemption Number in the space provided. The form does not ask for a Social Security number or FEIN. Your Agriculture Exemption Number is the identifier that matters.
Next, check every box that describes your operation. The categories track the statute: tilling and cultivating soil for crop production, raising livestock or poultry for sale, producing milk for sale, and specialty operations including aquaculture and ratite production. Check all that apply.
Below that, the form lists categories of exempt property: farm machinery, seeds and fertilizer, farm chemicals, feed and feed additives, livestock and poultry, fuel, water, and others. Check the boxes that match what you’re buying, or describe the specific items in the space provided.
Read the certification statement at the bottom before signing. Your signature affirms that you’re a qualifying farmer and that the items will be used in an exempt manner. The form warns that if you later put the property to a nonexempt use, you owe the tax immediately, measured by the original purchase price, remitted to the Department of Revenue in Frankfort.
What the Certificate Covers
KRS 139.480 defines the categories of property that qualify. Getting this right up front saves you from claiming an exemption on the wrong purchase and owing back taxes later.
Exempt purchases include:
- Farm machinery used exclusively and directly for tilling soil, raising livestock or poultry, or producing milk, along with attachments, repair parts, and replacement parts
- Livestock and poultry whose products ordinarily constitute food for human consumption, purchased for breeding or dairy purposes, or poultry for breeding or egg production
- Feed, pre-mixes, and feed additives for qualifying animals, including mineral blocks, protein supplements, milk replacer, and medicated feed pre-mixes
- Seeds whose products ordinarily constitute food for human consumption or are sold in the regular course of business, plus commercial fertilizer applied to farmland
- Insecticides, fungicides, herbicides, rodenticides, and other farm chemicals used in crop production or in raising qualifying animals
- Gasoline, special fuels, liquefied petroleum gas, and natural gas used exclusively and directly to operate farm machinery or qualifying on-farm facilities such as grain-drying, poultry, livestock, or dairy operations
- Water used in crop production, milk production, or raising qualifying animals
The statute explicitly excludes automobiles, trucks, trailers, and truck-trailer combinations from the definition of farm machinery, even when used on the farm. Administrative regulation 103 KAR 30:091 also keeps veterinary supplies (medicines, vaccines, vitamins, wormers) and veterinary instruments (needles, syringes, operating tables) taxable. Equipment used for lawn maintenance around a residence does not qualify, regardless of where on the property it is used. The general rule: if the item is not used exclusively and directly in the production process, it stays taxable.
Giving the Certificate to a Seller
Present the completed form to your vendor at or before the sale. The seller keeps it as legal proof they were justified in not collecting the six-percent tax. Retailers may accept paper or an electronic copy depending on their policies.
The blanket feature is the important part. Once a vendor has your completed certificate, it covers every qualifying purchase you make from that seller going forward. You do not fill out a new form each time. The certificate stays valid until you notify the seller in writing that it no longer is. If your Agriculture Exemption Number expires or you stop farming, that written notice is on you.
When You Need Form 51A159 Instead
Form 51A158 does not cover materials, machinery, or equipment that will be built into an on-farm structure. For construction, repair, or renovation of qualifying on-farm facilities such as grain storage buildings, poultry houses, livestock barns, dairy facilities, or aquaculture operations, use Form 51A159, the On-Farm Facilities Certificate of Exemption. Form 51A159 covers the building materials and equipment incorporated into the structure itself, including ventilation systems, feeding systems, and alarm systems. Form 51A158 covers the supplies used inside that facility once it’s built, such as feed, water, fuel, and chemicals.
Records, Audits, and Penalties
Kentucky’s statute of limitations for sales tax assessments is four years from the return due date or the filing date, whichever is later. If fraud is suspected, there is no time limit. Keep a copy of every executed Form 51A158 for at least four years. If the Department questions a purchase and you can’t produce a valid certificate, it can assess the unpaid tax, plus interest and penalties.
Misusing the exemption is a crime. Under KRS 139.990, executing an exemption certificate or using an Agriculture Exemption Number while knowing you’re not entitled to the exemption, or knowing the property won’t be used for the claimed exempt purpose, is a Class B misdemeanor. Separately, KRS 139.270 makes the purchaser financially liable for the full tax that should have been collected, and the Department can impose additional civil penalties on top.
The risk runs both ways. A farmer who buys fencing tax-free and then puts it around a residential yard rather than a pasture owes the tax. A non-farmer who borrows someone else’s exemption number to skip tax on a personal purchase faces the misdemeanor charge. The four-year audit window gives the Department plenty of time to catch either one.