Form 5472 Reference ID Number: How to Create and Use One
Updated June 2026 · Reviewed by a Form 5472 specialist
Updated June 2026 · Reviewed by a Form 5472 specialist
The short answer
Key takeaways
A reference ID number is a code you assign to identify a foreign related party that has no US taxpayer identification number. It is entered on line 4b(2) of Part II and can be up to 50 alphanumeric characters long.
Form 5472 must identify the foreign person who owns the US entity. When that person has a US TIN — an SSN, ITIN, or EIN — you simply enter it. But most foreign owners living abroad have never been issued any US number. For those parties, the IRS lets you supply a reference ID number instead: a code you make up yourself so the IRS can still track that specific party across filings.
The reference ID is not a government-issued identifier and carries no legal weight outside the form. Its only job is to give the foreign party a stable label. For the full field-level context, see the dedicated Form 5472 reference ID number page, and the line-by-line walkthrough in the Form 5472 instructions.
You need one whenever a foreign related party in Part II has no US TIN. Virtually every foreign-owned single-member LLC needs one, because the owner abroad has never been issued an SSN, ITIN, or EIN.
The trigger is simple: look at the foreign owner reported in Part II. If that person or company has a US taxpayer ID, enter it on the TIN line. If they do not, you must instead create a reference ID number — you cannot leave both blank. Because most foreign founders of a US LLC have never lived, worked, or paid tax in the United States, they have no US TIN, so the reference ID is the normal path.
| Foreign owner's situation | What goes in Part II |
|---|---|
| Has a US ITIN | Enter the 9-digit ITIN; no reference ID needed |
| Has a US EIN (foreign company owner) | Enter the EIN; no reference ID needed |
| Has no US TIN at all | Create and enter a reference ID number |
Source: IRS Instructions for Form 5472, Part II line 4. Verified June 2026.
Not sure whether you even have to file? Run through the 60-second qualifier first.
You assign it yourself. The only rule is a maximum of 50 alphanumeric characters with no special symbols. A practical format combines the owner’s name and country, such as JSMITH-CANADA-01.
The IRS imposes almost no formatting rules. The reference ID number must be 50 characters or fewer, use only letters and numbers (hyphens are commonly accepted, but avoid other punctuation), and be unique to that one foreign related party. Beyond that, the content is up to you. The goal is something memorable and stable that you will recognize next year.
| Rule | Detail |
|---|---|
| Maximum length | 50 characters |
| Allowed characters | Letters and numbers (no special symbols) |
| Uniqueness | One reference ID per foreign related party |
| Consistency | Reuse the identical code every year |
Source: IRS Instructions for Form 5472, reference ID number rules. Verified June 2026.
Filers often use the foreign owner’s initials plus country plus a sequence number — for example JSMITH-CANADA-01 or OWNER1UK2026. Avoid spaces and symbols like the ampersand or slash. Once you decide, write it on your filing checklist so it is never re-invented. When we prepare your return on the apply page, we generate and record a compliant reference ID for you.
It goes on line 4b(2) of Part II, the section identifying the 25% foreign shareholder. It does not go in Part I, which reports the US LLC and its own EIN on line 1b.
Part I of Form 5472 is about the US reporting entity — the LLC’s name, EIN, and business activity. Part II is about the foreign owner. The reference ID number belongs only in Part II, on the line that would otherwise hold the foreign party’s US TIN. Putting it anywhere else, or confusing it with the LLC’s EIN, is a common preparer mistake.
| Field | Part | What you enter |
|---|---|---|
| LLC's own EIN | Part I, line 1b | The 9-digit EIN of the US LLC |
| Foreign owner's US TIN | Part II, line 4b(1) | ITIN or EIN if the owner has one |
| Reference ID number | Part II, line 4b(2) | Your created code if no US TIN exists |
Source: IRS Form 5472, Parts I–II. Verified June 2026.
The full part-by-part map lives in the instructions guide.
The IRS requires the reference ID to be consistent across years for the same foreign party. Changing it on a later filing can make the IRS read it as a new party and create a mismatch on at least two returns.
A reference ID number only works as a tracking label if it never changes. The IRS instructions explicitly tell you to use the same reference ID number from year to year for the same related party. If you file JSMITH-CANADA-01 in 2025 and then switch to JS-CA-2026 the next year, the system may treat that as two different foreign owners — a data-quality problem that can flag the return for review.
The safest practice is to store the reference ID with your permanent records the moment you file, alongside the EIN and the mailing receipt. If you change preparers, hand them the exact code. Our service keeps your reference ID on file so every annual filing matches — start on the apply page.
A Form 5472 missing a required identifier is substantially incomplete, which the IRS treats as not filed. That triggers the $25,000 penalty per form, per year under IRC §6038A(d), with no cap and no statute of limitations.
The reference ID number is not optional decoration. When a foreign party has no US TIN, the reference ID is the only thing identifying that party — leave it blank and the form is incomplete. The IRS can treat a substantially incomplete Form 5472 as if it were never filed, exposing you to the full $25,000 penalty. After a 90-day IRS notice, an additional $25,000 accrues every 30 days, with no maximum.
Because there is no statute of limitations on an unfiled information return under IRC §6501(c)(8), a defective filing from a prior year can still be assessed today. Estimate the exposure with the penalty calculator, and read the full rule on the penalty page.
A foreign-owned single-member LLC cannot e-file. The pro forma Form 1120 with Form 5472 attached must be mailed to P.O. Box 149342, Austin, TX 78714-9342, or faxed to 855-887-7737 by April 15.
Even a perfectly completed reference ID number does no good if the form is filed the wrong way. There is no e-file path for a foreign-owned disregarded entity. The only two accepted methods are mail and fax, and the filing is due April 15 — or October 15 with a timely Form 7004 extension. Keep the certified-mail receipt or fax confirmation as proof.
| Method | Where | Proof to keep |
|---|---|---|
| P.O. Box 149342, Austin, TX 78714-9342 | Certified-mail receipt | |
| Fax | 855-887-7737 | Fax transmission confirmation |
Source: IRS Instructions for Form 5472 (foreign-owned U.S. DE). Verified June 2026.
Worried mail will be too slow? Compare the trade-offs in fax vs. mail, and confirm there is no shortcut in can you e-file Form 5472.
Form 5472 and pro forma 1120 — reference ID created, reviewed, and filed for a flat $299. Or message us first; we answer every question.