C/O (Care Of) Address on Form 1120 — The IRS-Approved Workaround

What 'C/O' Means on an IRS Form

"C/O" stands for "Care Of" — a centuries-old postal convention meaning "please give this to [the named third party] on behalf of [the addressee]." On Form 1120 and Form 5472, C/O is the IRS-approved way to route your tax mail through a third party while keeping your principal place of business as the actual address.

The Form 1120 instructions explicitly authorize this format: "If the corporation receives mail in care of a third party (such as an accountant or attorney), enter on the street address line 'C/O' followed by the third party's name and street address or P.O. box."

Exact Formatting on Form 1120 and Form 5472

On the principal address line of Form 1120 (and Form 5472 Part I, Line 1a), format like this:

Street Address: C/O [Third Party Name], [Their Street] City / State / ZIP: [Their location]

Example:

Street Address: C/O Smith CPA LLP, 1234 Main St City / State / ZIP: Wilmington, DE 19801

The LLC's actual operations might be in Berlin or Mumbai — but the IRS treats the C/O address as the official correspondence destination. The principal place of business remains conceptually wherever you actually operate; the C/O notation just routes mail.

Who Can Act as the C/O Recipient

The IRS instructions give two examples — "accountant or attorney" — but the actual scope is broader. Any third party who agrees to receive your mail and has a stable U.S. street address can serve as the C/O recipient.

Valid C/O recipients (in order of how clean they look on an IRS form):

1. Your CPA or enrolled agent — most defensible 2. Your attorney — equally defensible 3. A bookkeeping or tax-prep firm with a real office 4. A U.S. mailbox service with a street address (NOT a P.O. Box) — works but looks less professional 5. A U.S. friend or family member willing to forward mail — works in a pinch but raises questions in audit

Who can't act as C/O recipient: - The registered agent for your state of incorporation (the rule specifically excludes this) - A P.O. Box without a street address backing - A fictitious address or commercial mail-drop with no real presence

Why This Beats Using the Registered Agent Address

Three reasons to use C/O over the bare registered agent address:

1. Full IRS compliance. The Form 1120 instructions explicitly permit C/O; they explicitly prohibit the registered agent address. There's no ambiguity.

2. Better audit profile. If an IRS examiner pulls your file and sees a C/O notation, the optics are "taxpayer uses a professional service provider for mail handling" — a normal pattern. A bare registered agent address on the same line signals "this filer didn't read the instructions or is hoping no one notices."

3. Easier to explain on §6038A or transfer-pricing reviews. The C/O notation cleanly separates the operational address (where the business actually happens) from the correspondence address (where mail goes). The registered agent address conflates the two, making the entire address question harder to defend.