Dear Liz: I have several years missing from my Social Security earnings history, dating back to 1999. I have been filing income taxes jointly with my wife but we only kept our files for five years. How do I go about retrieving past income documents like my W-2s? I contacted Social Security and the IRS but can only get tax transcripts dating back to 2009.

Answer: Social Security says you ordinarily have three years to report mistakes. (Actually, being Social Security, it’s “three years, three months and 15 days.”) But you can correct mistakes further back if you have sufficient proof, such as tax forms, W-2s or pay stubs.

You can try contacting old employers to see if they can produce the W-2s you’re missing. Otherwise, write down as much as you can remember about where you worked, including the name of the employer, the dates you worked there and how much you earned. Then contact Social Security again, provide the information you’ve gathered and ask for help in filling in those missing years.

This is one reason why it’s smart to hang onto tax returns indefinitely. Even though you can (and probably should) shred backup documentation after seven years or so, you should keep copies of anything filed with the IRS, including W-2 forms.