Start with the RFC already in your records
You may have an RFC and still need a U.S. number for a business. The key is to name the business that needs the EIN, rather than searching for an “American RFC” for every transaction.
SAT’s guide distinguishes the 13-character RFC of a persona física from the 12-character RFC of a persona moral.SAT Keep the individual and company tax records separate when preparing your U.S. application.
Use your Constancia de Situación Fiscal to check the local record. SAT says it contains the RFC, name or company name, registered address and tax regime.SAT Compare those details with the Mexican party named in the U.S. request. A shop name should not replace the legal holder.
Keep the constancia as a local matching record, not a document that the IRS automatically requires for every EIN request. Its useful job here is to help you spot a personal RFC being confused with a company RFC, or an old address being copied into the application.
When a customer asks for a “tax ID,” ask for the actual form and field. It might be documenting the Mexican payee rather than asking you to form a U.S. LLC. Save that request before choosing an EIN or personal ITIN service.
Decide which business is applying
A Mexican business asking for a U.S. EIN and a new U.S. LLC owned from Mexico are different applicants. State the choice at the start of your request. If forming a U.S. entity, keep the accepted state record ready before the EIN step.
Make a one-page ownership record: Mexican individual or company, the U.S. entity if there is one, and the person who controls it. Add the actual business address and a reliable mailing address. A provider’s U.S. mail address should not replace your description of where the business operates.
The IRS online tool has location and responsible-party tax-ID requirements.IRS Living in Mexico does not stop you from requesting an EIN, but it can mean the international application route fits your facts better than the online tool.
Use the Form SS-4 instructions for the responsible-party entry if no SSN or ITIN is available.IRS Do not insert an RFC as though it were one of those U.S. numbers, and do not invent a number to complete an online screen.
Keep the Mexico treaty review separate
The IRS publishes the Mexico income-tax treaty, technical explanation and protocol materials.IRS Getting an EIN does not itself establish a treaty claim or give every payment the same treatment.
Article 14 specifically addresses independent personal services by an individual. Its conditions include a regularly available fixed base and time spent in the other country.IRS treaty For a Mexican consultant visiting a U.S. customer, keep the travel calendar and work arrangements. Do not apply that individual article automatically to a Mexican company invoice.
Keep the contract, payer request and residence details with the tax-form review. A service invoice, royalty and goods sale should not be merged simply because the customer is in the U.S. Tell the reviewer what the payment is for and who receives it.
For an individual foreign-payee form, review W-8BEN. For an entity request, establish its classification and the correct form before signing. Your local tax identifier and U.S. business EIN can appear in different records without either replacing the other.
Confirm whether a personal return creates an ITIN need. Owning a U.S. company, possessing an RFC and receiving a payer request do not automatically answer that question. Review the actual federal tax purpose with the application preparer.
Keep cross-border transfers visible
If your Mexican personal or company funds go into a U.S. LLC, label those transfers separately from customer revenue. Keep the date, amount, sender, recipient and explanation in the company ledger.
A foreign-owned U.S. disregarded entity may need related-party reporting through Form 5472 with a pro forma Form 1120.IRS Ask the reviewer to assess the transfers even if the new business has not sold anything.
Use matching date ranges when comparing Mexican records with the U.S. ledger. Keep the original currency visible rather than overwriting every source amount with a converted figure. Let the reviewer explain the conversion approach for the relevant filing.
Ask for a filing list for the U.S. entity and a separate review of Mexican obligations. An IRS number is not a clearance of the local business records. Keep both sets of adviser instructions with the documents.
Prepare the request from Mexico
- 1
Identify the RFC holder
Keep individual and company records separate, and match the legal name to the business that is applying.
Local records - 2
Name the U.S. applicant
State whether it is the existing business or a newly formed U.S. entity. Add formation details where relevant.
Entity - 3
Confirm the IRS route
Prepare the responsible-party details and actual business location before selecting the application method.
SS-4 - 4
Keep the EIN and filing records
Save the assignment notice and create a ledger for owner transfers and company activity.
After issue
Choose the next step with Nolly.com
Use the Nolly.com EIN service when the next step is the business tax number. Tell us whether you already have a company and whether an EIN has been assigned. That keeps a formation request separate from an EIN request for an existing business.
EIN registration
A U.S. tax ID for your company, even without an SSN.
Includes:
- Form SS-4 prepared for you
- Foreign address and owner handled correctly
- Filed with the IRS for you
- EIN confirmation letter sent to you
- Help by email and phone
Your questions answered
They identify taxpayers in different systems. Use the identifier requested by the actual form, not whichever number you already have.
An EIN request and company formation are different questions. Describe the existing company and its U.S. tax need before choosing formation.
This guide uses it to match Mexican local records, not as a universal IRS requirement. Check the RFC holder, legal name and address against the actual U.S. applicant.
An EIN is an identifier, not a treaty decision. Review the income and relevant treaty provisions separately.
More questions? See the full Nolly.com FAQ.
How we checked this
Every IRS fact on this page comes from IRS.gov or the other official pages listed below and was checked on October 3, 2026. Nolly.com's own prices are the only exception. Nolly.com is a private company and is not part of the IRS.
Nolly Services Inc, d/b/a Nolly.com, appears on the IRS page Acceptance agents – Canada. Nolly.com is a private company and isn't part of the IRS.
- Instructions for Form SS-4 (12/2025)https://www.irs.gov/instructions/iss4
- Get an employer identification numberhttps://www.irs.gov/businesses/small-businesses-self-employed/get-an-employer-identification-number
- SAT: Constancia de Situación Fiscalhttps://www.sat.gob.mx/portal/public/tramites/constancia-de-situacion-fiscal
- U.S.–Mexico income tax treaty: Article 14https://www.irs.gov/pub/irs-trty/mexico.pdf
- Instructions for Form 5472https://www.irs.gov/instructions/i5472
- SAT: CFDI guide, RFC formats for individuals and entitieshttps://www.sat.gob.mx/cs/Satellite?blobcol=urldata&blobkey=id&blobtable=MungoBlobs&blobwhere=1461173358220&ssbinary=true
- Mexico: tax treaty documentshttps://www.irs.gov/businesses/international-businesses/mexico-tax-treaty-documents
Checked against IRS.gov on October 3, 2026. General information, not tax advice.
