When filling out a Form W-9, there are typically no supporting documents that need to be attached. However, there are some situations where you may need to include additional documents or information. Here are some instances where attachments may be required:
1. Exemption Certification: If you are claiming an exemption from backup withholding, you may need to attach a valid exemption certification. This can include a valid Form W-8 series, such as a W-8BEN or W-8ECI, to establish your non-U.S. status.
2. Federal Identification Number: If you are providing an employer identification number (EIN) for your business instead of a Social Security number (SSN), you should attach a copy of your EIN confirmation letter received from the IRS.
3. Name Change: If your name has recently changed due to marriage, divorce, or other reasons, you might need to attach supporting documents such as a marriage certificate, divorce decree, or legal name change document.
4. S-Corporation Status: If you are a single-member limited liability company (LLC) electing to be treated as an S-Corporation, you should provide a copy of the IRS acceptance letter confirming your S-Corporation status.
5. Tax Treaty Benefits: If you are a non-U.S. resident providing services or earning income in the U.S. and claiming benefits under a tax treaty, you may need to attach a completed Form 8233 or a W-8BEN-E, along with any required supporting documentation, to establish your eligibility.
Remember, it's important to consult the official instructions provided by the IRS for Form W-9 or seek professional advice to ensure compliance with any specific attachment requirements based on your unique circumstances.