If I am mailing in my MA non-resident return, (and I checked off only official forms to be printed) it is including some federal forms, e.g. Federal form Schedule C. Am I actually required to mail those federal forms to MA???
The MA non-resident return instructions (see below) do not specifically say to include your federal Schedule C when paper filing your MA non-resident return. Make sure to include all the forms and schedules listed in bold in the instructions below.
According to the instructions for MA non-resident tax return Form 1-NY/PY (pg 21): "Be sure to include all five pages of Form
1-NR/PY and, if applicable, Schedule HC and all
other schedules.
Enclose with your Form 1-NR/PY, all state copies
of your Forms W2-, W-2G, PWH,WA, 2G, K-1 and
any Forms 1099 which included Massachusetts
withholding. If making a payment, go to mass.
gov/ dor/masstaxconnect for online payment options.
If you need to mail your payment, enclose a
check or money order payable to Commonwealth
of Massachusetts and be sure to sign the check
and write your Social Security number on it. Also,
be sure to use the light blue mailing label when
mailing your Form 1-NR/PY"
Click the screenshot below to view page 21 of the MA non-resident tax return instructions.
https://www.mass.gov/files/documents/2018/01/18/dor-2017-inc-form-1-nrpy-inst.pdf