Lots of replies, and most are misguided, so I'll add: I am a B2B SaaS business based outside the US. Tax withholding is not applicable between my customers and

Lots of replies, and most are misguided, so I'll add: I am a B2B SaaS business based outside the US. Tax withholding is not applicable between my customers and me, or at least it is not my responsibility. VAT is solved by reverse charge. I do have payment processing set up (with Braintree). The above AMEX requirements were on top of that — a completely separate procedure, just because AMEX feels different. As to the W8 BEN discussion, be careful with your biases: it might seem "obvious" to you that everyone needs to comply with whatever IRS requires of US businesses, if you live in the US. But I have customers in 44 countries. If you are American, before you state that something is obviously required, take a look at this (from recent E-mail): "Self-Certified Filled Form 10F will be required" "Permanent Account Number or Aadhaar Number of the assessee if allotted" "Period for which the residential status as mentioned in the certificate referred to in sub-section (4) of section 90 or sub-section (4) of section 90A is applicable" Still looks obvious? Those are from India, and I'm pretty sure these requirements seem totally obvious to my Indian customers.