If your father dies, you may need his Social Security number (SSN) in order to apply for survivor's benefits or to locate assets for a probate of his estate. Generally, you can locate this number in a person's files–on a tax return, for example. But if you can't find the number or don't have access to his personal papers, you can try running a search of the U.S. Social Security Death Index. You can also apply to the Social Security Administration for a copy of his Social Security record.

After your father dies, you can probably locate his SSN in his personal records if you have access to them. You may not be able to locate his Social Security card with the number on it, but other records are sure to have the number. For example, personal tax returns and employment and pay records will have his number on them.

Your father's attorney, executor, banker and investment banker will have his SSN. If he has a mortgage or credit card debt, you may be able to locate his SSN on these. Passport applications usually call for the SSN as well. Credit reports may contain his SSN.

If, for some reason, you don't have access to your father's personal papers and can't contact the professional persons he relied on during his lifetime, there are a few other options to try. To find the Social Security number for deceased parents, you can try using the Social Security Death Index.

The Social Security Death Index is a compilation of the Death Master File from the Social Security Administration. It is a database of all the deaths of people with SSNs that were reported to the SSA in the period 1935 through 2014. The reports were often made when family members filed for death benefits. In 2014, the law was changed to require a three-year delay before posting death records.

What kind of information can you get from the Death Index? Each file includes the following information if the SSA had the data:

• Last name
• First name
• Social Security number
• State issued
• Birth date
• Death date
• Last residence
• Lump sum payment

While you cannot access the Social Security Death Index through the SSA, you can access it online for a fee from Ancestry.com and free from Genealogy Bank (if you register) and from Family Search. Put in your deceased father's first, middle and last name and dates and locations of birth and death.

Apply to get your father's Social Security record from the SSA. You can use an online form called Request for a Deceased Individual's Social Security History, or download, print and mail in form SS-771. This record includes the person's Social Security application in addition to the SSN. The fee for this is currently under $30.