Well there's a good chance they will probably Accept it. Then you know you will have to amend the wrong 2020 return to change it to be for real 2020.
Do you need to file the 2018 W2? Did you file 2018 and need to amend to add this form? Or file an original 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. You can buy any version. All the Desktop programs have the same forms. You just get more help and guidance in the higher versions. Buy the download here
https://turbotax.intuit.com/personal-taxes/past-years-products
If you want to file for free you can fill out the forms by hand.
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
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
Prior year returns can only be printed and mailed. 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. And don't forget state.
Important! Mail Federal and State in separate envelopes and mail each year in separate envelopes.
