Any grant or stipend amount awarded in excess of tuition, required fees, books, and supplies is subject to federal income tax, as is any funding contingent upon providing service to the University (for example, teaching fellowships or research assistantships). Income taxes are not ordinarily withheld from stipend payments; be sure to incorporate this tax obligation into your financial planning.
If you have questions about US income taxes, visit the taxes page of Harvard's University Student Financial Services (SFS), where you will find information about federal and Massachusetts taxes, information specific to international students, access to Harvard-issued tax forms, and tax FAQs.
Please note that the 2019 federal and MA state tax filing deadline has changed to July 15, 2020.
Visit the IRS website for more information about the Economic Impact Payment (aka stimulus payment).