IRS Form 637 – In the complex world of excise taxes, businesses and individuals involved in specific activities must comply with IRS regulations to avoid penalties and access tax benefits. IRS Form 637, officially titled “Application for Registration (For Certain Excise Tax Activities),” serves as the key document for registering under relevant Internal Revenue Code (IRC) sections. Whether you’re a manufacturer, buyer, or producer dealing with fuels, chemicals, or other taxable items, understanding Form 637 is essential for seamless operations. This comprehensive guide covers everything you need to know about IRS Form 637, including who needs it, how to apply, and recent updates as of 2026. You can download the latest PDF version here: https://www.irs.gov/pub/irs-pdf/f637.pdf.
What Is IRS Form 637?
IRS Form 637 is an application used to register for excise tax activities under IRC sections 4101, 4222, 4662, and 4682. It allows eligible entities to engage in tax-free transactions, file claims for credits or refunds, or operate within the excise tax framework without upfront tax payments in certain scenarios. The form’s primary purpose is to ensure compliance while providing benefits like tax exemptions for registered activities.
The current revision of Form 637 is dated December 2025, reflecting updates to accommodate evolving excise tax rules, such as those related to clean fuels and chemical substances. Registration is mandatory before starting covered activities, and failure to register can result in significant penalties, including $10,000 for the initial failure and $1,000 per day thereafter.
Who Needs to File IRS Form 637?
Not everyone dealing with excise taxes requires registration, but specific roles and activities mandate it. You must file Form 637 if you are:
- Engaged in activities subject to federal excise tax under the specified IRC sections.
- Seeking excise tax benefits, such as tax-free purchases or sales, or the ability to file claims for refunds or credits.
Common entities include manufacturers, buyers, producers, importers, blenders, terminal operators, and ultimate vendors of taxable fuels, chemicals, vehicles, or equipment. For example:
- Pipeline or vessel operators in the bulk transfer/terminal system.
- Producers or importers of alcohol, biodiesel, renewable diesel, or clean transportation fuels.
- Buyers of items like taxable tires or sport fishing equipment for resale or export.
Each business unit with a separate Employer Identification Number (EIN) must submit its own Form 637. Individuals or sole proprietors use their Social Security Number if no EIN is available. Registration is not required for general taxpayers but is essential for those in regulated excise tax chains.
Activities Covered by IRS Form 637
Form 637 categorizes activities by letter codes, allowing applicants to register for one or more as needed. Below is a complete list of activity letters and their descriptions:
| Activity Letter | Description |
|---|---|
| A | Manufacturer of gas guzzler automobiles, sport fishing equipment (including fishing rods and fishing poles), fishing tackle boxes, bows, quivers, broadheads, points, arrow shafts, taxable tires, or vaccines. |
| B | Buyer of sport fishing equipment (including fishing rods and fishing poles), fishing tackle boxes, gas guzzler automobiles, bows, quivers, broadheads, points, or vaccines for further manufacturing or for resale to a buyer for further manufacturing. |
| C | Buyer of taxable tires for use on or in connection with the sale of another article the buyer manufactures and sells (1) for export, (2) to state and local governments, (3) to nonprofit educational organizations, or (4) as supplies for vessels or aircraft. |
| D | Buyer with a place of business in the United States purchasing vaccines, gas guzzler automobiles, taxable tires, sport fishing equipment (including fishing rods and fishing poles), fishing tackle boxes, bows, quivers, broadheads, points, or arrow shafts for export or for resale to a second purchaser for export. |
| E | Buyer (other than state or local government) of gas guzzler automobiles for ambulance, law enforcement, or firefighting. |
| F | Nonprofit educational organization, other than a public school; buying taxable tires, certain heavy vehicles, sport fishing equipment (including fishing rods and fishing poles), fishing tackle boxes, bows, quivers, broadheads, points, or arrow shafts for its exclusive use. |
| G | Persons making inventory exchanges of taxable chemicals under section 4662(c)(2) or persons selling or buying intermediate hydrocarbon streams under section 4662(b)(10). |
| I | Buyer (other than nonprofit educational organization or state or local government) of taxable tires for use on certain intercity, local, or school buses. |
| K | Buyer of kerosene for a feedstock purpose. |
| M | Blender of gasoline, diesel fuel (including a diesel-water fuel emulsion), or kerosene; producing a taxable fuel outside the bulk transfer/terminal system, including blenders of alcohol fuel mixtures, alternative fuel mixtures, biodiesel mixtures, and renewable diesel mixtures. |
| Q | First retail seller of certain heavy vehicles. |
| S | Enterer, position holder, refiner, terminal operator, or throughputter of gasoline, diesel fuel (including a diesel-water fuel emulsion), or kerosene, or industrial user of gasoline. |
| V | Manufacturer, importer, or buyer of ozone-depleting chemicals (ODCs) for export. |
| X | Pipeline operator or vessel operator (including certain deep-draft vessels) within the bulk transfer/terminal system. |
| Y | Buyer of kerosene for its use in commercial aviation (other than foreign trade). |
| AB | Producers and importers of agri-biodiesel. |
| AF | Producers and importers of alcohol. |
| AL | Alternative fueler that sells for use or uses alternative fuel as a fuel in a motor vehicle or motorboat. |
| AM | Alternative fueler that produces an alternative fuel mixture that is sold for use or used in the alternative fueler’s trade or business. |
| BC | Qualified blood collector organization buying taxable fuel, taxable tires, and certain heavy vehicles; claiming exemption from the communications tax and heavy highway vehicle use tax; or to claim a credit or payment of certain excise taxes, for its exclusive use in the collection, storage, or transportation of blood. |
| CA | Producers of clean transportation fuel that is sustainable aviation fuel (SAF). |
| CC | Credit card issuer that issues credit cards for sales of taxable fuel to a state or local government for its exclusive use or for sales of gasoline to a nonprofit educational organization for its exclusive use. |
| CN | Producer of clean transportation fuel that isn’t SAF. |
| NB | Producers and importers of biodiesel (other than agri-biodiesel) and renewable diesel. |
| QR | Qualified retailer of diesel fuel or kerosene sold in Alaska for nontaxable uses. |
| SA | Producers or importers of SAF. |
| SB | Producers of second generation biofuel. |
| UA | Ultimate vendor that sells kerosene for use in aviation. |
| UB | Ultimate vendor that sells undyed diesel fuel or undyed kerosene for use in certain intercity and local buses. |
| UP | Ultimate vendor that sells kerosene from a blocked pump. |
| UV | Ultimate vendor that sells (a) undyed diesel fuel or undyed kerosene to a state or local government for its exclusive use, or (b) gasoline (including aviation gasoline) to a state or local government for its exclusive use or to a nonprofit educational organization for its exclusive use. |
These activities span fuels, vehicles, chemicals, and equipment, ensuring targeted compliance.
How to Complete and Submit IRS Form 637?
Completing Form 637 requires accuracy to avoid delays. Start by entering your name, EIN (or SSN), address, and contact details. Indicate the activity letters you’re applying for and provide detailed responses in Part III about your business operations, such as annual volumes, facilities, and compliance history.
Required Additional Information
Attach supplemental sheets for each activity, including:
- Lists of products, volumes, or facilities.
- Certifications, IRS determination letters, or FDA registrations where applicable.
- Explanations for any penalties, convictions, or ownership changes.
Use additional pages for explanations, clearly marking your name and EIN on each.
Submission Methods
Fax the completed form and attachments to 855-887-7735 or mail to:
Department of the Treasury
Internal Revenue Service Center
Excise Operations Unit – Form 637
Mail Stop 5701G
Cincinnati, OH 45999
The IRS may require a bond and could conduct unannounced inspections during business hours.
Processing, Approval, and Status Check
Once submitted, the IRS reviews your application, which may take time depending on complexity. If approved, you’ll receive a Letter of Registration detailing your approved activities, effective date, and registration number. This letter—not a copy of Form 637—serves as proof of registration.
To check status, use the IRS’s Online Form 637 Registration Status Check tool at https://apps.irs.gov/app/exciseTax/. Registrations remain valid until revoked but require reregistration for significant ownership changes (over 50% in assets or stock). Notify the IRS of any changes within 10 days.
Recent Developments for IRS Form 637 in 2026
As of February 2026, key updates include:
- Expanded coverage for clean transportation fuels, requiring registration for producers claiming the clean fuel production credit under the One, Big, Beautiful Bill (effective for fuels produced after December 31, 2024, and sold by December 31, 2029).
- Safe harbors for sustainable aviation fuel (SAF) credits, updated in February 2024.
- Excise taxes on certain chemical substances under sections 4661 and 4671, updated in January 2022.
These changes emphasize environmental incentives, so producers of SAF or other clean fuels should review activity letters like CA, CN, and SA.
Conclusion: Ensure Compliance with IRS Form 637
Navigating IRS Form 637 is crucial for businesses in excise tax sectors to unlock benefits and avoid penalties. By registering promptly and maintaining accurate records, you can operate efficiently. For personalized advice, consult a tax professional. Stay updated via the IRS website, as regulations evolve. Download Form 637 today and start your registration process to stay compliant in 2026 and beyond.