On deadline day, fax beats mail: the 5472 package sent to 855-887-7737 with a transmission confirmation timestamped before midnight is a timely filing you can prove — the practical playbook is below. Nothing here changes what belongs in the package; it changes how confidently you can prove it arrived on time once the calendar has run out.

Key facts

  • Fax number: 855-887-7737 — the IRS's accepted fax line for the pro-forma 1120 + Form 5472 package (IRS: Instructions for Form 5472).
  • Mailing address, for context or as a backup: Internal Revenue Service, 1973 Rulon White Blvd, M/S 6112, Attn: PIN Unit, Ogden, UT 84201 (IRS: Where to file forms beginning with the number 5).
  • Scan and fax quality matters: the instructions call for a legible transmission — 300 DPI or better is the commonly cited standard — since a partially readable fax risks being treated as an incomplete filing (IRS: Instructions for Form 5472).
  • The deadline itself doesn't move: April 15, or October 15 with a timely-filed Form 7004 — fax and mail share the same due date; only the proof-of-timing mechanics differ (IRS: About Form 7004).
  • $25,000 per form, per year is what's at stake if the package doesn't arrive at all — the reason deadline-day mechanics get this much attention (IRS: Instructions for Form 5472).

Why fax wins under deadline pressure

Form 5472 cannot be e-filed by a foreign-owned disregarded-entity LLC — the complete filing walkthrough covers why — which leaves mail and fax as the two IRS-accepted channels. On any ordinary day, either works fine. On deadline day specifically, fax has one practical advantage that neither ordinary mail nor a rushed trip to a courier fully matches: it produces an immediate, self-generated confirmation showing the receiving number, the date, the time, and the page count, at the exact moment the transmission completes. Mail gives a shipping receipt if tracking was purchased, but no confirmation that the IRS itself has the package until, if ever, something comes back. A fax confirmation isn't a special legal shortcut — it's simply the strongest same-day evidence available that a complete package reached the IRS's fax line before the deadline passed. That's what matters when the October 15 deadline is hours away rather than weeks.

Pre-flight checklist (page order, the "Foreign-owned U.S. DE" legend, legibility)

A fax sent in a hurry is only as good as what's actually in it. Before dialing:

  • Order: the pro-forma Form 1120 goes first, Form 5472 immediately behind it — not the reverse.
  • The legend: confirm "Foreign-owned U.S. DE" is written across the top of the pro-forma 1120's first page — this is the routing cue the IRS's Ogden processing depends on, and it's the single most common thing a rushed filer forgets.
  • Completeness: every reportable-transaction category that applies is filled in, particularly the Part V contributions/distributions section disregarded entities routinely leave blank — see the full pro-forma 1120 walkthrough for the line-by-line detail.
  • Signature: an unsigned return is not a filed return, on fax day or any other day.
  • Legibility: scan at 300 DPI or better if faxing from a digital file; if faxing from paper, check that nothing is faint, cut off, or crooked in the feeder.
  • Page count: know exactly how many pages are being sent before sending them, so a short transmission confirmation is immediately recognizable as a problem rather than assumed to be fine.

Getting a fax confirmation that actually holds up later

Not every confirmation is equally useful months later if it ever matters. A confirmation worth keeping shows: the number dialed (855-887-7737), the date and time the transmission completed, the number of pages sent, and a success status — not just a mid-transmission status. On a physical machine, that's the printed transmission report; save or photograph it immediately rather than trusting the machine to hold onto it. On an online fax service, save the confirmation email or the service's own transmission log as a PDF the same day, not eventually — services vary in how long they retain records. Store the confirmation with the actual package that was sent, not in a separate folder that might not get connected back to this specific filing a year from now.

Failure modes (busy line, partial transmission) and safe retries

A busy signal is the easy case: retry, and note the time of each attempt if the clock is getting close to midnight. A partial transmission — the confirmation shows fewer pages received than were sent, or an error partway through — is not a filed return; treat it exactly as if nothing was sent, and resend the complete package again rather than trying to fax only the missing pages, which creates two incomplete transmissions instead of one. Keep every confirmation from every attempt, successful or not — a string of busy signals followed by one clean success is itself useful evidence of a good-faith, timely effort if the timing is ever questioned. If repeated attempts are failing as the deadline genuinely runs out, a mailed copy sent the moment mail becomes possible again, referencing the fax attempts and their timestamps, is a reasonable fallback — imperfect, but better than doing nothing.

After transmission: what to keep, what to calendar next

Once a confirmation shows success, keep three things together: the confirmation report itself, the exact package as sent (a saved PDF or a paper copy), and a short note of who sent it and when. Nothing else about this specific filing is due immediately. What belongs on next year's calendar, not this one: the recordkeeping requirement under IRC §6038A continues regardless of the filing being done, so the underlying transaction records still need to be kept, not discarded now that the form is filed. And if, despite a timely and provable fax, a penalty notice arrives anyway — it happens, usually from a processing mismatch rather than an actual late filing — the penalty and abatement guide covers exactly what a documented, timely transmission does for that conversation.

Frequently asked questions

Are online/internet fax services acceptable, or does it need a physical machine? The IRS's fax instructions don't distinguish by technology — a transmission reaching 855-887-7737 is what matters, not whether it originated from a physical machine or an internet/efax service. In practice, an efax service is often the more practical choice for an owner filing from outside the US, since it produces a digital confirmation record automatically and doesn't depend on finding a working physical fax machine.

What time zone does 'before midnight' refer to? The IRS does not publish a specific time zone rule for fax transmissions of this form. The safer practice is to treat the receiving line's local time — Mountain Time, since it terminates in Ogden, Utah — as the operative clock, and finish comfortably before that boundary rather than cutting it close against a home time zone's own midnight, which may already be several hours ahead or behind.

Is resending a duplicate transmission harmful? No. Sending the same complete package a second time, for example after an uncertain first attempt, is not a problem — the IRS receiving two copies of one genuine filing is a routine, harmless occurrence, not a red flag or a second filing that needs explaining. What actually causes problems is an incomplete package or an unresolved failed transmission left unaddressed.

Is it worth mailing a paper copy as backup too? Yes, when there's enough time to arrange it — sending a tracked copy by mail earlier in the week, with fax as the deadline-day fallback (or the reverse), gives two independent, timestamped records of a timely filing rather than one. On the literal last day, though, courier and priority-mail cutoffs have often already passed by the time deadline pressure sets in, which is exactly the gap fax is left to fill.

Written by Ifetoluwase Samuel Pirisola, Managing Director of Caldwell Tax Services, LLC — July 2026. General information, not tax advice for your specific situation. Start your intake if deadline day is close and you want a second set of eyes on the package before it goes out.

Sources: IRS: Instructions for Form 5472 · IRS: Where to file forms beginning with the number 5 · Glossary