What is the difference between an EIN and an ITIN?

All three are nine-digit US tax identification numbers, but they identify different things. An EIN (Employer Identification Number) identifies your business entity and is issued by the IRS via Form SS-4. An SSN (Social Security Number) identifies you as an individual and is issued by the Social Security Administration to US citizens, permanent residents, and non-citizens authorized to work in the US. An ITIN (Individual Taxpayer Identification Number) also identifies you as an individual, but is issued by the IRS to people who have a US tax filing obligation yet are not eligible for an SSN. In short: an EIN is for your company, while an SSN or ITIN is for you personally, and you will only ever have one of those two, never both. Non-US founders can get an EIN for their LLC without an SSN, and may separately need an ITIN if they have a personal US filing requirement. An EIN is an Employer Identification Number for businesses, while an ITIN is an Individual Taxpayer Identification Number for individuals who need a U.S. tax ID but are not eligible for an SSN.