After you file

I would file your return with the W-2 that you have now to avoid being late on your return. Depending on what information the new payroll company will change on your W-2, a W-2c will be issued to you if necessary. If they do send you a W-2c, you can then file an amended return. Amended returns do not “catch up” to your original return and replace them; they are processed as two separate returns.  

Amended returns have to be printed and filed by mail.  It can take the IRS up to 12 weeks or longer to process them.   If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it.  If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return. You can check the status of your amended return by clicking here: https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1