Did you make any Traditional or Roth IRA contributions during the year? It might be you had a 401K in the past and Turbo Tax is looking for that information to be entered in this year's return. Also check Box 12 of your W2 to see if there is anything listed with a code AA, D, E,EE, BB. These are all considered deferred compensation plans that you can receive a retirement saving credit.
There may be other reasons but these are the most likely suspects.
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