Where it goes
At the very top of the pro-forma 1120 cover sheet, as instructed by the IRS 5472 instructions. BorderFile adds it automatically; if you prepare the forms yourself, this label is routinely missed.
Why it matters
Without the “Foreign-owned U.S. DE” header the IRS may not route the attachment to the correct processing stream, and the filing may be rejected or require a follow-up. The requirement comes directly from the Form 5472 instructions published by the IRS; BorderFile’s preparation stamps the header automatically.
See also: pro-forma 1120, disregarded entity.