EIN for Mexican LLC Owners: The Tax Rule Your "Disregarded" LLC Doesn't Disregard

Three things before you apply. First, your LLC needs state approval -- applying before formation is complete is a common, avoidable delay. Second, keep your Mexican passport or INE handy in case the IRS asks for identity verification during a fax or phone follow-up. Third, decide your mailing address for the CP 575 confirmation letter -- a Mexican home address works, though many founders use a US virtual mailbox for faster, trackable delivery. One more decision worth making before you file: whether you will accept the LLC's default disregarded-entity status or actively elect corporate treatment via Form 8832, covered further down -- this affects Line 9a of Form SS-4, so it is worth deciding early rather than defaulting by accident.

The application process itself does not vary by country. Mexican founders use the same three non-resident routes as everyone else, since the IRS's online EIN system requires an SSN, ITIN, or US legal residence that most applicants do not have. Fax is the most reliable method: complete Form SS-4 and send it to 855-215-1627 if faxing from within the US, or 304-707-9471 from outside -- i.e., from Mexico -- with real-world turnaround commonly running one to two weeks despite the IRS's official four-business-day target. Phone, at 267-941-1099, is open to international applicants Monday through Friday, 6:00 AM to 11:00 PM US Eastern Time; Mexico's time zones run one to three hours behind Eastern depending on region, which still leaves a wide, comfortable calling window. Mail, at four to five weeks, is the slowest option and rarely worth choosing over fax.

A few fields on Form SS-4 consistently cause delays for non-resident applicants generally, Mexican founders included. Line 7b asks for the responsible party's SSN, ITIN, or EIN -- if you have none of these, the IRS's own instructions say to write Foreign or N/A, not leave the field blank, since a blank Line 7b is one of the most common reasons non-resident applications bounce back for correction. Lines 4a-4b need your full Mexican mailing address spelled out as Mexico rather than abbreviated, since that is where your EIN confirmation letter, Form CP 575, will be mailed if you apply by post. Line 9a asks about entity classification -- this is the field tied directly to the Article 4-B question above. Accepting the default disregarded-entity box is simpler on the US side; actively filing Form 8832 to elect corporate treatment is a separate decision covered in the section below, and getting Line 9a wrong without understanding the difference can complicate both your IRS filings and your Mexican tax timing later.

Once issued, your EIN arrives with a confirmation letter, Form CP 575, sent by fax, mail, or both depending on your application method -- keep it permanently, since banks and payment processors will ask for it during account opening. A lost CP 575 cannot be reissued, but the IRS will provide an EIN Verification Letter, Form 147C, as a substitute for any future banking or tax need. From here, most Mexican founders move on to opening a US bank account -- Mercury and Relay both work for Mexico-based founders, since Mexico is not on either provider's restricted list -- and, since almost every non-resident-owned single-member LLC counts as a foreign-owned disregarded entity, filing Form 5472 alongside a pro forma Form 1120 annually, regardless of whether the LLC had US activity that year. The $25,000 minimum penalty for missing that filing applies independently of the Article 4-B question -- they are two separate compliance obligations, one to the IRS and one, potentially, to the SAT.

If a formation service is handling your EIN application, confirm that the responsible party listed on Line 7a is you, the actual owner -- not a staff member at the formation company. The IRS defines the responsible party as whoever ultimately owns or controls the entity's funds and decisions, identified by their real name and passport-based nationality. An EIN record that lists someone other than the actual owner creates a mismatch that can complicate matters later if a bank or payment processor needs to verify beneficial ownership, which is the same information reported separately under BOI/FinCEN rules. If a provider suggests listing anyone but you, treat it as a red flag rather than a convenience, regardless of how routine it sounds.

Because Article 4-B's accrual rule applies specifically to entities that are transparent for tax purposes, some Mexican-owned LLCs explore electing corporate tax treatment on Form 8832 instead of accepting the default disregarded status. In principle, an LLC taxed as a corporation is not a transparent entity, which could change when Mexican tax applies to its profits -- shifting from an annual accrual regardless of distribution toward a model closer to how Mexico taxes a genuine foreign corporation. In practice, this trades away the LLC's US pass-through simplicity: a corporate election exposes the LLC to US federal corporate tax at 21% on its own income, on top of whatever Mexican tax applies when profits are eventually distributed to you personally, plus a 60-month lock-in period once elected. Whether that trade is worthwhile depends entirely on how much profit the LLC retains versus distributes, and on numbers a Mexican accountant needs to run for your specific situation -- this is not a box to check on Form SS-4 without that conversation happening first. The math tends to favor staying disregarded for founders who distribute most of what the LLC earns each year -- there is little undistributed profit for Article 4-B to reach, so the accrual rule has little to bite on. It tends to favor at least evaluating a corporate election for founders who deliberately retain earnings inside the LLC to reinvest -- a common pattern for bootstrapped SaaS or e-commerce businesses reinvesting into ads, inventory, or hiring -- since that retained profit is exactly what Article 4-B accumulates to your personal Mexican tax return whether or not you ever touch it personally.

Most non-resident founders assume a disregarded single-member LLC means no home-country tax until they withdraw money. For a Mexican tax resident, that assumption runs straight into Mexico's Income Tax Law (LISR). Article 4-A treats a foreign entity that is fiscally transparent in the jurisdiction where it was formed -- which is exactly what a US single-member LLC is under the IRS's default disregarded-entity classification -- as a foreign transparent entity for Mexican purposes. Article 4-B then requires Mexican tax residents to accumulate, on an accrual basis, their share of that entity's income every year, whether or not a single peso or dollar was actually distributed. The rule specifies that control is not relevant -- ownership alone triggers it, not board votes or day-to-day management. None of this changes your IRS paperwork: Form SS-4 does not ask about LISR Article 4-B. But it does change when Mexican tax becomes due, and that is worth knowing before you form the LLC, not after your accountant raises it at filing season. This is not a brand-new rule invented for LLC owners specifically -- Articles 4-A and 4-B have been part of the LISR framework since well before 2020, and recent 2026 legal commentary confirms they remain actively applied. It also does not mean a US LLC is a bad structure for a Mexican founder; plenty of Mexican-owned LLCs operate for years without issue. It means the "form the LLC, worry about Mexican tax later" sequence that works for founders in treaty-light countries does not work the same way here, because the trigger is the LLC's transparent classification itself, not the absence of a treaty.

A few mistakes show up repeatedly. Assuming a disregarded LLC means no Mexican tax obligation until money is withdrawn, when Article 4-B taxes undistributed profits annually regardless. Not knowing that Mexico requires its own informative filing for residents receiving income through foreign transparent entities or preferential-regime jurisdictions -- a separate obligation from anything the IRS requires, with real consequences for skipping it, worth confirming current requirements with a Mexican accountant rather than assuming the rule has not changed since it was first introduced. Leaving Line 7b of Form SS-4 blank instead of writing Foreign, which remains one of the most frequent reasons the IRS returns a non-resident application for correction. And electing corporate treatment on Form 8832 as a reflexive workaround to the Article 4-B question without running the actual numbers on US corporate tax exposure versus the Mexican tax timing benefit -- a decision that can cost more than it saves if made without that comparison. Conflating the US-Mexico tax treaty, in force since 1994, with protection from Article 4-B is another recurring mix-up. The treaty addresses double taxation on income that is actually recognized and sourced under both countries' rules -- it does not exempt undistributed LLC profits from Mexico's transparent-entity accrual regime, since that regime is a domestic anti-deferral rule, not a treaty question. Founders who read that a treaty exists and assume it covers every cross-border tax question end up missing Article 4-B entirely until it shows up on a return.