I am a non-US resident living in Hong Kong, and have recently received some corporate bond coupon payments. Since I forgot to fill out a W-8BEN form to declare my non-US residence status, 30% of the payments was withheld by IRS. I was wondering if anyone knows the process of and the IRS forms used to claim back these withholding taxes. Thanks.

Provide the W-8BEN to the payor of the interest and file Form 1040NR for a refund.