What Form W-7 is
irs.gov says to use Form W-7 to apply for an IRS individual taxpayer identification number (ITIN), and that you can also use it to renew an ITIN that is expiring or has already expired. An ITIN is a 9-digit number issued by the IRS to individuals who are required for U.S. federal tax purposes to have a U.S. taxpayer identification number but do not have and are not eligible to get a Social Security number. RepeatForm does not tell you whether you qualify.