My 2018 taxes show its for the year 2019, but I haven't not filed my 2019 taxes, will this be an error I can fix?

You cannot use TurboTax Online to file a 2018 tax return.  Only current year returns (2019) can be filed electronically using TurboTax Online.

If you entered your 2018 information into TurboTax Online and electronically filed the return, then what you do next will depend on whether the return was accepted or rejected by the IRS.

If the return was rejected, you will need to essentially delete all the information regarding income and deductions that you entered and enter your 2019 tax information instead.  Then you can electronically file the 2019 return.

If the return was accepted, you will need to create and mail an amended return for 2019.  Again, in the amended return you will delete all the 2018 information that was entered and replace it with the 2019 information.

In order to use TurboTax to create and file your 2018 return, you will need to purchase and download a 2018 version of the program.  This return will need to be mailed to the IRS for processing.

See the following TurboTax article for more details:  How do I prepare a prior year return?

@trinity770