From the IRS itself…
The IRS will begin accepting tax returns on [Jan. 30] after updating forms and completing programming and testing of its processing systems. This will reflect the bulk of the late tax law changes enacted Jan. 2. The announcement means that the vast majority of tax filers — more than 120 million households — should be able to start filing tax returns starting Jan 30.
But if you’re filing for residential energy credits, depreciation of property or general business credits, you’ll have to wait even longer, possibly not until March. The deadline remains April 15.