Indiana diverges from the federal calendar in three places that catch filers: the corporate return is due in May, pass-throughs file in April (not the federal March date), and the individual extension runs to November 16. Every one of Indiana’s 92 counties also levies a local income tax.

Indiana Tax Deadlines at a Glance (2026)

Three corrections CPAs should note. The C-corporation IT-20 is due May 15, 2026 — the 15th day of the 5th month — not April 15. The IT-20S and IT-65 pass-through returns are due April 15, 2026, not the federal March 16. And the individual extension runs to November 16, 2026 (the statutory November 15 rolls off a Sunday), not October 15.

All 92 Counties Levy a Local Income Tax

Indiana’s Local Income Tax (LIT) is universal — all 92 counties impose one, not just “many.” It is reported on the state individual return via Schedule CT-40, with rates set by each county and adjusted in January and October. This is a required part of every Indiana resident’s return, so confirm the correct county rate from Departmental Notice #1.

Rates and the Elective PTET

Indiana’s flat individual income tax rate is 3.00% for the 2025 tax year (filed in 2026), dropping to 2.95% for 2026 on a legislated glide path. The corporate income tax rate is 4.9%. Indiana offers an elective pass-through entity tax (PTET) at the individual rate, letting S corporations and partnerships pay at the entity level for SALT-cap relief; the annual election is made on the IT-20S or IT-65. PTET estimated payments follow a 20th-of-the-month schedule (April, June, September, December).

Estimates, Extensions, and Penalties

Individual estimated payments are due April 15, June 15, September 15, 2026, and January 15, 2027. A valid federal extension automatically extends the Indiana filing deadline to November 16; without one, file Form IT-9. Pay at least 90% by April 15 to avoid the late-payment penalty (interest still accrues). The late-payment penalty is 10%, failure-to-file is 20%, and the 2026 interest rate is 7%.

CPA Action Steps

• Use May 15 for the C-corp IT-20 — not April 15

• File IT-20S and IT-65 in April, not on the federal March date

• Confirm the correct county LIT rate on every individual return

• Note the individual extension runs to November 16

Verify current rates and dates against the Indiana Department of Revenue (in.gov/dor) before filing.