CASDI is a state tax. It is deductible on Schedule A if you itemize your deductions and opt for state tax.
As you did not itemize, you do not need to amend your tax return. No further action is needed and you just keep the form W-2C in your tax records.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"