The Social Security Number (SSN) is a unique identification number assigned by the U.S. Social Security Administration (SSA) to individuals, which is used to track individuals' income and social security benefits. The following are the rules and specific examples for the generation of U.S. Social Security numbers： ### 1. **Basic structure** -**Format**: SSN consists of 9 digits and is usually divided into three parts: `AAA-GG-SSSS`. -'AAA`: The first three digits, called the ”Area Number" (Area Number), indicate the geographic area where the number is assigned. -'GG`: The middle two digits, called the ”Group Number" (Group Number), are used for number allocation in further subdivided regions. -'SSSSS': The last four digits, called the ”Serial Number" (Serial Number), represent a unique number in a specific region and group. ### 2. **Area code (AAA)** -The area code indicates the geographic area where the number was originally assigned. Each state and territory in the United States has a specific number range. For example： -001-003: New Hampshire -004-007: Maine -008-009: Vermont -and many more. -Over time, the rules for the allocation of area numbers have changed, and they no longer strictly correspond to specific geographic areas. ### 3. **Group number (GG)** -Group numbers are used to further subdivide number allocation in specific regions. The group numbers are from 01 to 99, but they are not allocated continuously, but in a certain order and rules. ### 4. **Serial number (SSSS)** -The serial number is the last four digits, indicating a unique number in a specific region and group. Serial numbers range from 0001 to 9999. ### 5. **Special rules** -**Invalid number**: Some number combinations are considered invalid, such as： -000, 666, 900-999 area codes. -00 group number. -0000 serial number. -**Randomization**: Since 2011, SSA has adopted a randomized allocation method and no longer allocates numbers based on geographic areas. ### 6. **Specific examples** -**Valid SSN**: `123-45-6789` -Area code: 123 -Group number: 45 -Serial number: 6789 -**Invalid SSN**:`666-12-3456` -Area code: 666 is considered invalid. ### 7. **Precautions for use** -**Privacy protection**: SSN is highly sensitive personal information and should be carefully protected to avoid leakage. -**Identity verification**: SSN is commonly used in scenarios such as identity verification, tax declaration, employment, and bank account opening. ### 8. **Social Security numbers of other countries/regions** -**Canada**: The format of the social insurance number (SIN) is `123-456-789`. -**United Kingdom**: The format of the National Insurance Number (NINO) is `AB123456C`. -**Australia**: The format of the tax number (TFN) is `123 456 789`. Understanding the structure and rules of social security numbers helps to better manage and protect personal information while avoiding potential fraud risks.