Individual filers
• April 15 — Form 1040 and tax payment due • October 15 — Extended return due (Form 4868 must be filed by April 15) • April 15 — IRA & HSA contributions for prior year
Quarterly estimated taxes
Q1: April 15 • Q2: June 15 • Q3: September 15 • Q4: January 15 (following year). Self-employed, investors, and S-corp owners typically must pay quarterly to avoid underpayment penalties.
Business filers
• March 15 — S-corp (1120-S) and partnership (1065) returns • April 15 — C-corp (1120) returns • January 31 — W-2s and 1099-NEC due to recipients and IRS