March 1 – Farmers and fishermen who did not make 2017 estimated tax payments must file 2017 tax returns and pay taxes in full.
March 2 – Automatic extension deadline for employers and health care providers to provide Forms 1095-B and 1095-C to individuals.
March 15 –
- 2017 calendar-year S corporation income tax returns are due.
- 2017 partnership returns are due.
- Deadline for calendar-year corporations to elect S corporation status for 2018.