Every 2019 W-2 that you received must be reported on your 2019 tax return, even if they are for small amounts. Remember that each one of those W-2’s has your Social Security number on it, and that income was reported to the IRS by the employer. You do not want to get in trouble with the IRS for under-reporting your income.
ALL of your W-2’s must be entered on the SAME tax return.
W-2's come from your employer, and they have until Jan. 31 to issue it. Some employers allow you to import the W-2 through the software, but often you still need information from the actual W-2 just to import it. So waiting for your employer might be your only choice now.
https://ttlc.intuit.com/questions/1934390-how-do-i-import-my-W-2
https://ttlc.intuit.com/questions/2588751-why-can-t-i-import-my-w-2
Yes, you can go back and add more later on. Obviously do not file your return until all of your W-2's (and other tax information) have been entered.
@MisterBill Sorry--- users can only add W-2's easily to tax returns that have NOT been e-filed yet. If they e-filed and left out W-2's, it's a whole big deal and it is no picnic.