What happens if you mail file your federal and then also e-file your federal so that you can e-file the New York State taxes

Unfortunately, the IRS will no longer allow us to paper-file the federal return and efile the state.  The system is set up to reject state efile attempts if the federal tax return was not efiled.

Most likely, the E-files will both be accepted before the mailed return gets to the IRS. 

whichever gets there first will be processed. you can efile successfully as long as the paper file still hasn't been received. once it has then it will just produce an error in the efile process.

so you can go ahead and efile your state after efiling your federal. if nothing has changed between the paper federal file and efile then there is no risk of complication. if you changed anything then you might need to make sure you amend the paper file to match the information used in the efiled state form.

citation: just got off the phone with a turbo tax rep who says he used to work for the irs.