An Individual Taxpayer Identification Number (ITIN) is a unique nine-digit number issued by the Internal Revenue Service (IRS) to individuals who need to file taxes in the United States but do not qualify for a Social Security Number (SSN). ITINs are primarily used by non-resident aliens, their spouses, and dependents to ensure they can comply with tax laws. ITINs help individuals report their income and pay taxes, even if they are not eligible for an SSN. This number is essential for anyone who has tax obligations in the U.S., allowing them to access tax benefits and file returns accurately.