You may also check with:

• The Harvard Tax Office to find out about your tax liabilities and possible tax treaty implications: (p) 617-496-5224. Provides guidance on a range of related topics. 
• The Harvard International Office (HIO). Provides excellent information for international scholars, including access to the tax software Sprintax (for non-resident aliens)
• A presentation on Sprintax is available here: darryl_z_sprintax_presentation.mp4

3 more resources: 

• The National Postdoc Association provides an Overview of Tax Issues for Postdocs.
• Vita tax clinics, a volunteer organization that has a branch at Harvard Law School. Please note that appointments are made on a first come, first serve basis, so you need to get there early.
• The IRS itself!