W2 Mate will create 1099 e-File submissions that comply with IRS publication 1220 (flat text file for electronic filing). You can then upload the submission file to the IRS through the FIRE system (
https://fire.irs.gov/).
Please remember that you need to register with the IRS in order to obtain a TCC (Transmitter Control Code) to submit the file that is created within the W2 Mate software to the IRS.