I was common law married to my ex for 10 years before we married for two years before divorcing. He died last year. I have a child by him who was born the first year in our common law marriage. My question is: I am trying to claim his benefits and they want proof of common law marriage. I thought it would be easy since we filed our tax returns together but have since found out you can only go back 4 years for the transcripts. We were common law married in the 90's. Any suggestions?
Establishing proof of a common-law marriage is problematic at best, particularly if one of the parties is deceased. Social Security basically ends up making their determination on the length and validity of a common-law marriage on a case by case basis. Social Security will likely want to have a form SSA-753 (https://www.ssa.gov/forms/ssa-753.pdf) completed by at least one of your ex-husband's blood relatives in order to verify your allegations about the marital relationship, and they will also want any documentation that you can submit to confirm that the relationship existed for at least 10 years. Copies of joint tax returns are one example of the types of documentation that could be used, but other legal documents such as mortgages or contracts showing you as husband and wife could also be used. Pretty much any dated document that you can come up with that shows both of your names and indicates that you considered yourselves married would bolster your claim. I assume that your divorce decree only lists the date of your formal marriage, so that probably won't be helpful in establishing that you met the 10 year duration of marriage requirement for surviving divorced spousal benefits.
Each state has it's own rules regarding common-law marriages, which are outlined in the following section of Social Security's operations manual: https://secure.ssa.gov/apps10/poms.nsf/lnx/0200305075, and the development guidelines used by Social Security to document a common-law marriage are covered in the following section of the manual: https://secure.ssa.gov/apps10/poms.nsf/lnx/0200305065, so you might want to review that for ideas.
About the only thing that I can suggest you do is file your claim and submit any evidence that you think might be helpful in proving the fact and duration of your common-law marriage. Social Security will then make their determination and notify you of their decision. If their determination is unfavorable, you will then have appeal rights.