This is the case in many european countries. European VAT IDs are usually recorded in some kind of publicly accessible registry and usually build by prefixing I

This is the case in many european countries. European VAT IDs are usually recorded in some kind of publicly accessible registry and usually build by prefixing ID of tax payer with country code. For example in czech republic: - everyboby has "birth number", which is more or less equivalent of SSN except it in clearly encodes gender and for most people also DOB. - corporations and any entity that is licensed for trade (including sole proprietorships) have "ICO" (which somewhat funilly translates into "personal identification number"), in essence it is equivalent to US's EIN. - any entity which directly deals with tax office has DIC (tax identification number), which for natural persons is "CZ" + birth number and for other entities is "CZ" + ICO, same string is also an EU-wide VAT ID. Once you start a bussiness or even own part of non-tradeable public company (which includes things like homeowners association) all three of these numbers are readily available in various open access government registries, together with first and last name and usually with registered address and thus nobody uses knowledge of one of these numbers as serious authenticator (but from time to time it is used as kind of filter for who given bussiness is willing to deal with).