WHOA!! You can not use Turbo Tax online to do 2018. It is only good for 2019. You have a big problem. Hope that it rejects.
Online is only for 2019 returns. If you actually submitted and filed your 2018 info then you have to wait until the IRS starts taking returns on Jan 27 and see if it is Accepted or Rejected. If it Rejects you can change it around to be for 2019 and resend it. BUT if it is Accepted then you need to wait for the IRS to fully process your return and you get the first refund or pay the tax due. Then you can fill out an Amended Return 1040X. So if you have filed DO NOT change or enter anything else into your return until you find out if you have to amend.
Again DO NOT CHANGE or enter anything into your return if you already filed. You will have to start the Amended return with the original return that was filed. How to amend 2019
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27577
When you efile you get back 2 emails. The first email only confirms the transmission and the second email says if it was Accepted or Rejected.
You can check your efiling status here,
https://turbotax.intuit.com/tax-tools/efile-status-lookup/
Then you still need to file a 2018 return. You can only buy the download for prior years. You have to buy a separate program for each year. They only sell the last 3 years. You need a full Windows or Mac computer to install it on. Buy the download here
https://turbotax.intuit.com/personal-taxes/past-years-products/
You have to print and mail prior year returns. When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS received the return. Don’t forget state.
Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.
Or If you have a simple return You can fill out the blank forms for free.
Here is the IRS 2018 Form 1040
https://www.irs.gov/pub/irs-prior/f1040--2018.pdf
And 2018 Instructions https://www.irs.gov/pub/irs-prior/i1040gi--2018.pdf
2018 Tax and EIC Tables https://www.irs.gov/pub/irs-prior/i1040tt--2018.pdf
IRS 2018 Schedules 1 thru 6 (only if needed)
Sch 1 : https://www.irs.gov/pub/irs-prior/f1040s1--2018.pdf
Sch 2 : https://www.irs.gov/pub/irs-prior/f1040s2--2018.pdf
Sch 3 : https://www.irs.gov/pub/irs-prior/f1040s3--2018.pdf
Sch 4 : https://www.irs.gov/pub/irs-prior/f1040s4--2018.pdf
Sch 5 : https://www.irs.gov/pub/irs-prior/f1040s5--2018.pdf
Sch 6 : https://www.irs.gov/pub/irs-prior/f1040s6--2018.pdf
