It is too late to prepare or e-file a tax return for free online.
Online tax preparation and e-filing for 2018 returns is now permanently closed. You had until midnight on Tuesday, October 15 to finish and attempt to e-file; if your e-file was rejected you had until October 20 to make corrections and re-file. Now it is too late to use online software or to e-file. If you have any changes/corrections at all to make to your 2018 return, you now have to complete it using desktop software, which you must download to a full PC or Mac (not to a mobile device).
If you already paid for your online software you can ask customer support for a download of the desktop software.
They are available from 5 a.m. to 5 p.m. Pacific time Monday-Friday.
If you are getting a refund, there is no penalty for filing late. If you owe tax due, then file and pay the amount due as shown on the Form 1040, but expect a bill later from the IRS for the penalty and interest you will owe. Only the IRS will calculate this—TurboTax will not calculate it.
If you want to prepare it for free then you can prepare the return on paper and mail it in.
The tax forms are different for 2018 and beyond since the new tax laws went into effect. Everyone gets a "postcard size" Form 1040 that only goes to line 23. In addition, there are six possible extra pages called "schedules" that may be included as part of the tax return that you prepare and file.