Yes, you should amend your tax return.
Code A means Uncollected social security or RRTA tax on tips reported to your employer.
Code D means Contributions to your 401(k) plan (including a simple 401(k) plan).
Please see this TurboTax article for instructions on how to amend your tax return in TurboTax.
I'm trying to go back on this website to amend my tax return, but I can't find the section with the drop down menu to choose the letter in 12a-12d anywhere.
Actually I should have chose DD, which is nontaxable.
It's on your W-2, so go to Personal Income or Wages & Income->Wages and Salaries->Wages and Salaries, and select the W-2 you want to work on.
Just to add some information about amending a previously filed return, before amending your return you will need to wait until such return has been accepted by the IRS. You can amend a return only after it has been filed and accepted by the IRS. E-filed returns are considered filed when you have received notice from the government that your return has been accepted. If your return has been rejected, it is not considered filed.
Mailed returns are considered filed the date you post your return.
When you are ready to amend, you can access your previously filed return, in TurboTax online, from the TurboTax home page. Scroll down the screen to the section Your tax return & documents. If you have used TurboTax CD/download, then you can amend your previously filed return by selecting Other Tax Situations, and then scroll down to Other Tax Forms.
Here is a link to a TurboTax article that explains in greater detail the process to amend a previously filed return. How to Amend my Federal Tax Return for a Prior Year