May 24, 2018 17:42 Updated Follow The tax basis is the portion of your DC account contribution that was taxed at the time it was paid into your account. Related articles How will my DROP benefits be taxed when I retire? How does a lump sum payment at retirement affect my taxes? How does a post-retirement rollover to an IRA or qualified plan at retirement affect my taxes? I am planning on submitting my retirement application before the new online retirement application comes out. Which application should I be using? When do I get my retirement benefit?