What is a W-9 and a W-8 and is there a difference between the two?
The W-9 series is used to report your tax ID number.
The W-9 is used for anyone with a tax ID number (SSN or ITIN) and basically says, “Hey IRS/Treasury, this is my Tax ID number!” Many banks are now requesting this document because of FATCA reporting requirements. Since they are required to report the assets of their American customers to the US, the W-9 or W-8 (in rare cases) is best suited for that.
Even though the W-9 is just a reporting document (you are not taxed on anything), if you are not caught up on your US filing regulations (i.e., tax returns and FBARs), it could cause trouble. Coming forward to the IRS to voluntarily become compliant is better than having your bank provide that information to the IRS. Otherwise, it could appear that you are hiding something and raise a red flag.
The W-8 series is used to certify that the filer is not an American citizen or resident.
Even though there are many of these, usually US citizens or residents won’t encounter them at all – they’re used most often by non-residents with US-sourced income.