Louisiana runs a full month behind the federal calendar — nearly everything is due May 15 — and its pass-throughs do not follow the federal March date. The 2025 reforms also flattened both income taxes and repealed the corporate franchise tax.
Louisiana Tax Deadlines at a Glance (2026)
Entity Type | Return Due | Extended Due Date |
|---|---|---|
Individuals (IT-540) | May 15, 2026 | November 15, 2026 |
C Corporations (CIFT-620) | May 15, 2026 | November 15, 2026 |
S Corporations (CIFT-620) | May 15, 2026 | November 15, 2026 |
Partnerships (IT-565) | May 15, 2026 | November 15, 2026 |
The correction to note: Louisiana pass-through returns are due May 15, 2026 — not the federal March 16. Every Louisiana return, including partnerships (IT-565) and S corporations (which generally file the CIFT-620), aligns to the state’s May 15 deadline, with an automatic six-month extension to November 15. Louisiana’s later-than-federal calendar is one of its defining features.
The 2025 Flat-Rate Reforms
Louisiana’s 2024 special session overhauled its income taxes effective for 2025: the individual income tax is now a flat 3% (replacing the graduated 1.85%–4.25% brackets), and the corporate income tax is a flat 5.5% (replacing the graduated 3.5%–7.5% structure). Additionally, the corporate franchise tax is repealed for periods beginning on or after January 1, 2026 — a significant simplification for Louisiana entities.
Elective PTE Tax
Louisiana was one of the earliest PTE-tax states (Act 442 of 2019). The elective pass-through entity tax now applies at the flat 3% individual rate, letting owners work around the federal SALT cap. Watch a 2026 change: S corporations that file a composite return are barred from making the PTE election for periods beginning on or after January 1, 2026.
Estimates, Extensions, and Penalties
Individual estimated payments (IT-540ES) follow the standard quarterly schedule — April 15, June 15, September 15, 2026, and January 15, 2027. Louisiana grants its extension automatically (no form), but it extends filing only, not payment. The delinquent-filing penalty is 5% per month (maximum 25%), plus a delinquent-payment penalty and interest from the original date.
CPA Action Steps
Use May 15 for every Louisiana return, including pass-throughs — not the federal March date
Apply the new flat 3% individual / 5.5% corporate rates for 2025
Note the corporate franchise tax repeal (2026)
Check the composite-filing restriction on the PTE election for 2026
Verify current rates and dates against the Louisiana Department of Revenue (revenue.louisiana.gov) before filing.