An Individual Taxpayer Identification Number, or ITIN is for taxpayers who don't qualify for a Social Security number. It's 9 digits long and looks like a Social Security number, except it always begins with the number 9.
ITINs are used exclusively for filing tax returns. They don't entitle the taxpayer to Social Security benefits, stimulus payments, or other benefits.
To apply for an ITIN, complete IRS Form W-7, IRS Application for Individual Taxpayer Identification Number. Form W-7 requires documentation substantiating foreign/alien status and true identity for each individual.
You can mail the W-7 and documentation to the address in the Form W-7 Instructions. Bring it to your local IRS office, or use an acceptance agent (colleges, financial institutions, or accounting firms that are authorized by the IRS to assist applicants in obtaining ITINs). They'll review the W-7 and documentation before sending it to the IRS.
Form W-7(SP), Solicitud de Número de Identificación Personal del Contribuyente del Servicio de Impuestos Internos is available for Spanish speakers.