You may have been asked to fill out a W-8BEN-E with the IRS and then received a notice from the IRS along with your EIN# stating that your 1120F needs to be filed by June 15.
File an extension which will add another 6 months to your current filing due date:
Fill out form 7004 and mail it to:
Internal Revenue Service
P.O. Box 409101
Ogden, UT 84409
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