How can I attain a TCC number to efile 1042-S forms?
Its easy. This link
https://www.irs.gov/pub/irs-pdf/f4419.pdf
takes you to Form 4419 which is the Application for Filing Information Returns Electronically (FIRE). Question 7 on Form 4419 asks you to select which forms you are efiling. Select 1042-S and any other forms. The TCC number to efile 1042-S forms is different from the TCC number to electronically file the 1099 or W-2 or 1095 forms. Fill the form out and then mail to:
Internal Revenue Service
230 Murall Drive, Mail Stop 4360
Kearneysville, WV 25430
Or fax using one of the below numbers:
(877) 477-0572 (within the U.S)
(304) 579-4105 (International)
I recommend faxing and not mailing. Mail is slow. The IRS typically emails or calls or faxes back the TCC number and then mails the transmitter control code as well, but the mail takes many weeks to arrive.
by 
Erich J. Ruth
Erich J. Ruth provides technical support for National Software which is the parent company for 1099FIRE. 1099FIRE develops and markets a comprehensive range of products that enables any size of business or institution to effectively manage and comply with year-end filing requirements. 1099FIRE is an employee-owned company located in Phoenix, Arizona.
If you have any questions or comments about our software, feel free to contact us at any time.