if you are using the online app you are preparing your 2019 return NOT 2018. if you submitted it, it will be rejected because of the 2017 W-2. as a matter of fact online prep and e-filing for 2018 are closed. to prepare your 2018 return you need the desktop software. it must be mailed in.
The current online program is only for 2019 returns -- no other year. And even if you accidentally put the wrong W-2 in, it is not filed unless you clicked a big orange button that said "transmit my returns now." As has already been mentioned, even if you did that, it would likely be rejected.
If you need to file a 2018 return:
Online preparation and e-filing for 2016, 2017 and 2018 is permanently closed.
To file a return for a prior tax year
If you need to prepare a return for 2016, 2017, or 2018 you can purchase and download desktop software to do it, then print, sign, and mail the return(s)
You may also want to explore purchasing the software from various retailers such as Amazon, Costco, Best Buy, Walmart, Sam’s, etc.
Remember to prepare your state return as well—if you live in a state that has a state income tax.
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/state received the return.
Note: The desktop software you need to prepare the prior year return must be installed/downloaded to a full PC or Mac. It cannot be used on a mobile device.
If you are getting a refund, there is not a penalty for filing past the deadline. If you owe taxes, the interest/penalties will be calculated by the IRS based on how much you owe and when they receive your return and payment. The IRS will bill you for this; it will not be calculated by TurboTax.