Income (taxable and exempt per a treaty benefit) and taxes withheld, will be reported to foreign individuals on IRS Form 1042-S Foreign Person's U.S. Source Income Subject to Withholding
IRS Form 1042-S Foreign Person's U.S. Source Income Subject to Withholding is mailed to individuals by March 15 of the following tax year
IRS Form W-2 Wage and Tax Statement is mailed to individuals by January 30 of the following tax year

Are Nonresident Aliens required to file a U.S. income tax return?

Nonresident aliens receiving payments classified as U.S. Source income must file a tax return with the Internal Revenue Service. See IRS Publication 519 for more information
Nonresident aliens receiving payments classified as U.S. Source income must file a tax return with the Commonwealth of Massachusetts. See the Massachusetts Department of Revenue web site for more information