Individual Taxpayer Identification Numbers (ITINs) that have not been used when filing a tax return at least once in the past three years will automatically expire on Dec. 31, 2017. There’s also a rolling expiration date affecting certain ITINs. The key number to look for is in this position: 9xx-XX-xxxx. If your ITIN has the middle digits of 70, 71, 72 or 80, you’ll need to renew it before the new year.