....The IRS hasn't announced when they will start accepting yet. In the past 10 years or so, they haven't started until ~ 3rd week in January. One or twice not until the end of Jan.
BUT...for SE folks it could be longer, depending on what forms are needed and when the IRS actually finalizes all their draft forms. Boomark the following URLs to check for when TTX finalizes their software versions of the various Fed and State tax forms. Some may be finalized later than others.
In any case.....Don't file before ~1 Feb, or only after you get ALL of your tax reporting documents or you will regret filing earlier.
And don't file early! Last year (for 2018) the IRS put out some late changes and some early filers got tax due notices after they got their refund. Also if you file in an early batch they get stuck in processing and might even take longer to get your refund.
And You should wait because you might get a late W2 or 1099 in the mail. They have until Jan 31 to send you the tax forms. Or they may send you a corrected W2 or 1099 even later.