Regular Expressions Cookbook

4.12. Validate Social Security Numbers

Problem

You need to check whether someone entered text as a valid Social Security number.

Solution

If you simply need to ensure that a string follows the basic Social Security number format and that obvious, invalid numbers are eliminated, the following regex provides an easy solution. If you need a more rigorous solution that checks with the Social Security Administration to determine whether the number belongs to a living person, refer to the links in the section of this recipe.

Regular expression

^(?!000|666)(?:[0-6][0-9]{2}|7(?:[0-6][0-9]|7[0-2]))-↵
(?!00)[0-9]{2}-(?!0000)[0-9]{4}$

Regex options: None

Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

Python

if re.match(r"^(?!000|666)(?:[0-6][0-9]{2}|7(?:[0-6][0-9]|7[0-2]))-↵
(?!00)[0-9]{2}-(?!0000)[0-9]{4}$", sys.argv[1]):
    print "SSN is valid"
else:
    print "SSN is invalid"

Other programming languages

See Recipe 3.5 for help with implementing this regular expression with other programming languages.

Discussion

United States Social Security numbers are nine-digit numbers in the format AAA-GG-SSSS:

• The first three digits are assigned by geographical region and are called the area number. The area number cannot be 000 or 666, and as of this writing, no valid Social Security number contains an area number above 772.

• Digits four and five are called the group number and range from 01 to 99.

• The last four digits are serial numbers from 0001 to 9999.

This recipe follows all of the rules just listed. ...