If I have already filed my taxes and stated that I (incorrectly) cannot be claimed as a dependent, but I actually can be claimed as such, what can I do to fix this error?

[DoninGA · Accepted solution]

You will need to amend the 2018 tax return to change your dependency status.  An amended federal tax return, Form 1040X, can only be printed and mailed, it cannot be e-filed.  The IRS will take up to 4 months or longer to process the amended tax return.  If taxes are owed after completing the amended return, you send a check with the amended return when it is mailed.  If the amended return has a tax refund, then the IRS will send you a refund check in the mail for the refund, the refund cannot be direct deposited.

The tax return should not be amended until the tax refund has been received from the IRS.

The IRS Form 1040X is estimated to be available on 03/07/2019.  See this TurboTax website for IRS forms availability - https://care-cdn.prodsupportsite.a.intuit.com/forms-availability/turbotax_fed_online_individual.html

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed