After you file

Yes, you can claim the 2018 credit by filing Form 1040X to amend your 2018 return. 

To amend your return, follow these steps:

1. Click on this link to download the correct version of our free amendment software TurboTax 2018 Amendment Software.
2. Install the TurboTax 2018 software on your computer.
3. Sign into your return at TurboTax.com with the user ID and password used to file your 2018 tax return.
4. Look for Your tax returns and documents and click Show
5. Select Download .tax file.  Save this file to a folder where you can easily find it. 
6. Launch the TurboTax program.  If it doesn't automatically detect your file, click on File and then Open Tax Return and then navigate to the folder where you saved your .tax file to select it. 

Now that you have the tax return double-check that it is exactly the same as the return that you filed before proceeding. 

1. As a best practice, save a copy of your tax file.  Use the Save As command (Duplicate if using a Mac) to create a new file with a unique name such as  My 2018 Tax Return Amendment.
2. Follow the instructions on the screen to begin the amendment process.
3. Add the information about the income and tax paid that was not on the prior year return (don't duplicate the income if it was already there and you are just adding the tax paid.)
4. Proceed to the Review tab to review the return.
5. Print the return and mail it to the address that prints with the return. 

Note that amended tax returns can only be filed by mail and may take 12-16 weeks to process under normal circumstances.  Processing times may currently be longer due to reduced staffing at the IRS. 

Approximately three weeks after you mail your return, you can track the status on the IRS website here: Where's My Amended Return?

In your case, since unused credits can be carried forward to 2019, I recommend preparing the 2018 amendment before finalizing and filing the 2019 tax return in case you need to input any credit carry forward amounts into the 2019 return.