Then that's what you should report. Still, I can imagine DD looking like D 17. TT says, "The "17" in code D17 refers to a contribution made for 2017 and is a redundant indication since code D by itself on a 2017 W-2 already means a contribution for 2017. Ignore the "17" and select code D from TurboTax's drop-down box. [This doesn't quite explain your situation because it refers to a 2017 W2, but it gives a pretty good hint.]" It appears this would be related to last year, so your D17 is from one tax year (not this one) and the D is for this tax year (no need for an 18). So, you should type the D17 in, but select "D" from the drop-down box, which you also will select for 12c.
