Wet Ink Signature Required for Mailed IRS Returns (Form 1120 + 5472)

What 'Wet Ink' Means

A wet ink signature is one made by physically applying pen to paper. The IRS uses the term to distinguish it from typed names, scanned signatures, copy-pasted PNGs, or e-signatures created in DocuSign or Adobe Sign.

For mailed returns, the IRS expects a wet ink signature on Form 1120 in the 'Sign Here' block on page 1. The signer is the LLC's responsible party — typically the sole foreign owner. You sign with a pen, on the actual sheet of paper you're about to mail.

Why Wet Ink Matters for Mailed Returns

The IRS requires a 'valid signature' under §6061 to treat a return as filed. For e-filed returns the IRS accepts electronic signatures via Self-Select PIN or Practitioner PIN. For faxed returns, the IRS has confirmed (in IRM 3.42.5 and related guidance) that on-screen or embedded electronic signatures are acceptable, since the fax transmission itself is treated as an electronic signature.

For MAILED returns, the IRS treats the paper as the original. A signature that's only a digital image — added to the PDF before printing — can be challenged as 'not a true original signature.' The safe path is to print the form, sign it with a real pen, and mail the physical signed copy.

Common Mistakes That Invalidate the Signature

Four mistakes the IRS has flagged:

A. Typing your name in a script font (like Lucida Handwriting or Brush Script) instead of signing. Typed text — regardless of font — is not a signature.

B. Pasting a scanned image of your signature into the PDF, printing it, and mailing the print. The IRS treats this as a photocopy, which is not an original signature.

C. Signing in light pencil. Pencil can be erased or fade, and isn't permanent. Use dark blue or black ink.

D. Signing on the wrong line. The signature block on Form 1120 is specifically labeled 'Sign Here' with a line for signature, a line for printed name, and a line for date. All three must be completed.

Who Can Sign on Behalf of the LLC

The signer must be a person authorized to bind the LLC. For a single-member LLC owned by one foreign person, that's almost always the owner themselves.

If you've authorized a CPA, enrolled agent, or attorney via Form 2848 (Power of Attorney and Declaration of Representative), they can sign on your behalf — but a generic power of attorney from your home country is NOT sufficient. Form 2848 is the only POA the IRS accepts for tax signing authority.

If the LLC is owned by a foreign corporation rather than an individual, the signer should be an officer of that corporation authorized to sign U.S. tax documents on the corporation's behalf.

Faxing vs Mailing: Which Signature Rule Applies?

If you fax: An electronic signature embedded in the PDF (drawn on screen, traced with a stylus, or pasted from a signature image) is fully accepted. The fax transmission itself constitutes the electronic delivery.

If you mail: The IRS expects a wet ink signature on the paper that arrives. Print the form, sign in pen, mail the original. Don't sign electronically, print, and mail — that's a printed image of a signature, not a real signature.

The safest combined approach for foreign owners with no easy access to U.S. mail: fax the return with an electronic signature. This avoids the wet ink issue entirely while still satisfying §6061. See our submission guide for the IRS fax number.