Mississippi follows the federal calendar and is in the middle of two tax phase-downs. For the 2025 tax year, individual and C-corporation returns are due April 15, 2026, and pass-through returns are due March 16, 2026. The individual rate is now a flat 4.4% on income above an exemption, while the corporate franchise tax is still in effect and scheduled for repeal in 2028.

What are Mississippi's 2026 tax filing deadlines?

For the 2025 tax year, the Mississippi individual return (Form 80-105) and C-corporation income and franchise return (Form 83-105) are due April 15, 2026. The pass-through entity return (Form 84-105), which covers both S-corporations and partnerships, is due March 16, 2026, since the statutory 15th-day-of-the-third-month date falls on a Sunday.

What are Mississippi's 2025 tax rates?

The Mississippi individual income tax exempts the first $10,000 of taxable income and taxes the remainder at a flat 4.4% for 2025, with a further cut to 4.0% scheduled for 2026. The corporate income tax is graduated: 0% on the first $5,000, 4% on the next $5,000, and 5% above $10,000. The corporate franchise tax remains in effect at $0.75 per $1,000 of capital, with a $25 minimum, dropping in 2027 and repealed in 2028.

How does Mississippi's extension work?

Mississippi honors the federal extension automatically; attach a copy of the federal extension to reach October 15, 2026. The extension is to file only, so tax is still due April 15, 2026. Businesses use Form 83-180 for the corporate extension.

What is Mississippi's pass-through entity (PTE) election?

Mississippi lets an S-corporation or partnership elect to be taxed at the entity level, which moves the deduction above the federal SALT cap. The election is available for 2025, made by filing Form 84-381 and checking the electing box on the Form 84-105. The electing entity is taxed at the corporate graduated rate of 0%, 4%, and 5%, not the individual flat rate, which is a point to model before electing.

How does Mississippi tax nonresident pass-through owners?

Nonresident owners with no other Mississippi activity may elect to join a composite return, and once elected they continue filing that way. Where a nonresident owner does not consent or file individually, the entity becomes liable and remits at the 5% top marginal rate on that owner's Mississippi-source share.

How does a firm handle Mississippi at scale?

Two moving parts to watch. First, the pass-through date is March 16, a month before the individual and corporate returns, so track it separately. Second, the rates are changing yearly, with the individual rate dropping to 4.0% in 2026 and the franchise tax winding down through 2028, so projections built on this year's numbers need updating. Carry the current-year rates into each client model and flag the PTE election before March. See how we think about scaling tax prep workflows.

Where do these dates come from?

All deadlines and thresholds here trace to the Mississippi Department of Revenue. Verify against the source before filing.