Does anyone know if we need to register for a tax number to sell our books (ebooks or paperback) via KDP on Amazon or anywhere else? I read on another ebook publisher that it is required but the KDP site doesn't seem to mention it, unless I missed something. Thank you in advance. Has anyone published an ebook on KDP and had to apply for a tax number?
You cannot set up a KDP publishing account without entering your home-country tax ID. For Americans, that is almost always the Social Security number; for Brits, the National Insurance number; and so on. The US Internal Revenue Service no longer issues a special number (the EIN) for this purpose, though some people abuse the system and do just that. But only if you use your home-country tax ID can the correct withholding be calculated by the tax interview.
(Don't trust KDP to publish a print edition. Don't trust CreateSpace to publish an ebook. Each does one thing well and the other thing poorly.)