Part I: Identification of Applicant
The legal name for which the EIN was secured, trade name, EIN, telephone and fax numbers, mailing address, and the street address if a P.O. box is used or the street address differs.
637
Application for Registration (For Certain Excise Tax Activities)
- Agency
- IRS
- Revision
- Rev. December 2025
- Fillable fields
- 50
- Pages
- 7
- Official source
- IRS form page
- Checked
- October 21, 2026
Form 637: Application for Registration (For Certain Excise Tax Activities)
Form 637, Application for Registration (For Certain Excise Tax Activities), is the application a business or individual sends to the IRS to be registered for certain excise tax activities. The form says it is used to apply for excise tax registration for activities under sections 4101, 4222, 4662, and 4682. Each activity has a letter on the Activity Letter chart printed on the form, from A for manufacturers of certain taxable articles to UV for certain ultimate vendors of fuel.
The applicant lists its activity letters in Part II, answers the general questions in Part III and attaches the additional information the chart asks for under each letter. The form says the application must be reviewed and approved before the applicant is registered, bond may be required, and the review may include inspection of the premises during normal business hours without advance notice. An approved applicant receives a Letter of Registration showing its activities, the effective date and its registration number.
The instructions are printed on the form itself, after the Activity Letter chart. You can fill out the PDF free in your browser on this page and download it without an account.
What's on Form 637
Part II: Activities
The activity letter from the chart and a brief description of each activity applied for, with the Additional Information Required for each activity attached.
Part III, Section A: all applicants
Lines 1a to 7 ask about Form 720 filing, earlier applications, revoked or suspended registrations, the business start date and activity, related entities, addresses, books and records, owners and officers, and a contact person.
Section B: all fuel applicants
Line 8, for fuel activities K, M, S, X, Y, AB, AF, AL, AM, CA, CC, CN, NB, QR, SA, SB, UA, UB, UP, or UV, describes ownership changes in the past 2 years, or "None."
Section C: certain fuel applicants
Lines 9 to 14, for activities K, M, S, or Y, ask about penalties under chapter 68, convictions under chapter 75 or felonies involving theft, fraud or false statements, tax under section 4103, and earlier revocation.
Signature and Activity Letter chart
A signature under penalties of perjury by a person with authority to bind the applicant, followed by the chart listing each activity letter and the additional information it requires.
How to fill out Form 637
- 1
Have an EIN
Part I asks for the EIN. The instructions say an EIN can be applied for online at www.irs.gov/EIN, or by faxing or mailing Form SS-4 to the IRS.
- 2
Complete Part I
Enter the legal name the EIN was secured for, any trade name, phone, fax and mailing address. The instructions say to show a P.O. box only if the post office does not deliver mail to the street address.
- 3
Pick the activity letters
In Part II, enter the letter and a brief description for each activity from the chart, and attach the additional information listed for that letter. Write the name and EIN on each attached sheet.
- 4
Answer Part III
Answer every question in Section A and attach sheets for lines 2b through 6 as needed. The form says to explain why if a question doesn't apply. Fuel applicants also complete Section B, and K, M, S or Y applicants answer Section C, explaining any "Yes."
- 5
Sign
A person with authority to bind the applicant signs, prints their name and enters a title and date. The instructions list who signs for individuals, partnerships, LLCs, corporations, government agencies, tax-exempt organizations, estates and trusts.
- 6
Reregistering
The instructions say a reregistration after an ownership change is a newly completed Form 637 with the current registration number entered on line 1d.
Why fill Form 637 on indox
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- Fill the form right in your browser, no software to install
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Where to send it, review and changes
Where to apply
The form says to fax Form 637 to 855-887-7735 or send it to Department of the Treasury, Internal Revenue Service, Excise Operations Unit, Form 637, Mail Stop 5701G, Cincinnati, OH 45999.
Review and approval
The application is reviewed and approved before registration, and bond may be required. The form says a copy of Form 637 isn't a Letter of Registration, and a denial is sent in writing with the reason.
Complete information
The form says processing is delayed if not all of the required information is sent. The IRS will ask for more information if needed, and more can be provided at any time.
Penalty for failure to register
The form says the penalty for failure to register, for those required to register, is $10,000 for the initial failure and $1,000 for each day following, unless the failure is due to reasonable cause.
Changes after registration
The form says to notify the IRS office within 10 days if any information submitted changes, such as an address or business activities. Registration status can be checked at https://apps.irs.gov/app/exciseTax/.
Reregistration for fuel activities
For fuel activities under section 4101, the form says a change of more than 50% of the ownership of a registrant calls for reregistration. It doesn't apply to companies whose stock is regularly traded on an established securities market.
Related forms
720
Quarterly Federal Excise Tax Return
715 fields, 8 pages
SS-4
Application for Employer Identification Number
89 fields, 2 pages
8849
Claim for Refund of Excise Taxes
27 fields, 4 pages
4136
Credit for Federal Tax Paid on Fuels
485 fields, 4 pages
8864
Biodiesel, Renewable Diesel, or Sustainable Aviation Fuels Credit
32 fields, 1 page
6627
Environmental Taxes
282 fields, 2 pages
Who files Form 637?
The applicant, the entity or individual named with its employer identification number in Part I, completes the form, and a person with authority to bind the applicant signs it. It goes to the IRS Excise Operations Unit.
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Questions about Form 637
Is a copy of Form 637 proof of registration?
No. The form says a copy of Form 637 isn't a Letter of Registration. If the application is approved, the IRS issues a Letter of Registration with the activities, the effective date and the registration number.
Where is Form 637 sent?
The form says to fax it to 855-887-7735 or mail it to the Excise Operations Unit, Mail Stop 5701G, Cincinnati, OH 45999.
Does Form 637 have separate instructions?
The IRS page links no separate instructions. The General Instructions are printed on the last two pages of the form, after the Activity Letter chart.
Who signs Form 637?
A person with authority to bind the applicant. For a corporation, the form lists the president, vice-president, treasurer, assistant treasurer, chief accounting officer, or any other officer duly authorized to act for the corporation.
What is the penalty for not registering?
The form says $10,000 for the initial failure and $1,000 for each day following, for those required to register, unless the failure is due to reasonable cause.
How is a registration's status checked?
The form points to https://apps.irs.gov/app/exciseTax/ to confirm the status of a registration. Applying for another activity or canceling a registration goes through the IRS office where the business is registered.