The Social Security Death Index (SSDI) is a widely used collection for modern genealogical research. It contains information provided by the Social Security Administration (SSA) for individuals (with Social Security numbers) who died between 1962* and the present. The SSDI often provides the following information about a deceased individual.
By knowing just the first three digits of someone's SSN, you can correctly guess their birth state. The nine-digit SSN has been used since 1936 to track a person's wages for the purpose of accruing benefits with the Social Security Administration. The SSN has 3 sections.
Area Numbers
The first three digits of the SSN are called the area numbers. This is because they originally corresponded to the state that a person lived in at the time they were issued their SSN.
Beginning in 1972, the area numbers began being assigned based upon the zip code in the mail address to which the individual requested his or her card to be sent. Thus, it is possible for someone to reside in one state but ask that the card be returned to another states, thus rendering the area number less than area specific.
Group Numbers
Digits four and five in the SSN are referred to as group numbers. They identify the block of numbers currently being issued. As an example, the SSNs 123-01-0001 through 123-01-999 would all be issued before moving on to the next group number.
Serial Numbers
Digits six through nine are known as serial numbers. They are issued consecutively from 0001 to 9999.
By dissecting someone's SSN you can learn the state in which they lived when they applied for the number for those SSNs issued prior to 1972 and the state noted in the return address for those applied for after 1972.
In some cases, letters may appear after a social security number . For example, I have a California death certificate that reports a social security number with an "A" appended to the end of the number. For example: "000-00-0000A."
The Social Security number followed by one of these codes is often referred to as a claim number. The SSA assigns these codes once someone applies for benefits. These letter codes may appear on correspondence from Social Security or on a Medicare card. They will never appear on a Social Security card.
For example, if the wage earner applying for benefits and your number is 123-45-6789, then their claim number is 123-45-6789A. This number is also be used as their Medicare claim number, once they become eligible for Medicare.
Code
Identification
A
Primary claimant (wage earner)
B
Aged wife, age 62 or over
B1
Aged husband, age 62 or over
B2
Young wife, with a child in her care
B3
Aged wife, age 62 or over, second claimant
B5
Young wife, with a child in her care, second claimant
B6
Divorced wife, age 62 or over
BY
Young husband, with a child in his care
C1-C9
Child - Includes minor, student or disabled child
D
Aged Widow, age 60 or over
D1
Aged widower, age 60 or over
D2
Aged widow (2nd claimant)
D3
Aged widower (2nd claimant)
D6
Surviving Divorced Wife, age 60 or over
E
Widowed Mother
E1
Surviving Divorced Mother
E4
Widowed Father
E5
Surviving Divorced Father
F1
Parent (Father)
F2
Parent (Mother)
F3
Stepfather
F4
Stepmother
F5
Adopting Father
F6
Adopting Mother
HA
Disabled claimant (wage earner)
HB
Aged wife of disabled claimant, age 62 or over
M
Uninsured – Premium Health Insurance Benefits (Part A)
M1
Uninsured - Qualified for but refused Health Insurance Benefits (Part A)
T
Uninsured - Entitled to HIB (Part A) under deemed or renal provisions; or Fully insured who have elected entitlement only to HIB
TA
Medicare Qualified Government Employment (MQGE)
TB
MQGE aged spouse
W
Disabled Widow
W1
Disabled Widower
W6
Disabled Surviving Divorced Wife
http://blog.genealogists.com/2012/12/anatomy-of-social-security-number.html
