Louisiana tax guide

Louisiana Income Tax Filing: IT-540, May 15 Date, Flat Rate

Updated October 8, 2026

Louisiana residents file Form IT-540 and report all income. Nonresidents and part-year residents file IT-540B and report Louisiana income only. Calendar-year returns are due May 15, not April 15. The state gives an automatic six-month extension with no form, but the tax is still due on the original date.

How Louisiana taxes your income

Louisiana changed its tax structure recently. For tax years 2025 and beyond, the Department of Revenue says the state uses a flat rate for all income, replacing the old graduated structure. If you are comparing a 2025 return to an older one, do not carry over the old brackets.

Who files what depends on residency.

Residents file Form IT-540 and report all income, including earnings from other states. The Department says a temporary absence from Louisiana does not change your domicile.
Nonresidents and part-year residents file Form IT-540B and report only Louisiana-source income. The return uses a ratio of your Louisiana adjusted gross income to your federal adjusted gross income to find the taxable amount.

If you paid tax to another state on income that is also on your Louisiana return, residents get a credit for the net tax paid there. The credit is claimed on Schedule C. Keep a copy of the other state's return.

May 15 and the automatic extension

Louisiana does not use the April 15 federal date. The Department says individual returns are due by May 15 for calendar-year filers. Fiscal-year returns are due on the 15th day of the fifth month after the fiscal year ends.

The extension is automatic. Under the state's statute, you get six months to file, and no paper or electronic form is needed. That is the whole process, so there is nothing to submit to ask for it.

The extension covers filing only. The Department says it does not allow more time to pay. Tax not paid by the original date picks up interest and a late payment penalty. The Department also lists an Income Tax Extension Payments resource, so use it if you want to send what you expect to owe.

The IRS keeps its own April 15 date and the same pay-on-time rule. Our extension guide shows both.

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Filing and paying on LaTAP

The Louisiana Taxpayer Access Point, called LaTAP, is the Department's online system. It lets you file your return, make a payment, check your refund and manage your account.

The Department lists these payment routes.

Credit or debit card.
Electronic funds transfer.
Payment plans and installment agreements, which you request from the Department yourself.

Its Where's My Refund page is the place to check status. The individual income tax resource list also names a school expense deduction, a school readiness credit and a way to request innocent spouse relief. Both may matter to families with children, so look at them before you file. Anything about payment plans or innocent spouse relief involves the Department directly, and a qualified professional who does representation can advise you on it.

Military families and Louisiana

Louisiana has real choices for military families. For tax years beginning January 1, 2023 or later, military personnel and their spouses can each elect one of three places for tax purposes.

Their residence or domicile.
Their spouse's residence or domicile.
The service member's permanent duty station.

Before 2023, a person with a Louisiana domicile reported all income no matter where they were stationed.

Active-duty members who are stationed outside Louisiana for a long stretch of consecutive days can qualify for an income deduction. The Department caps it, so check the instructions for the limit and the number of days. The Department also has a page for military personnel who are stationed in Louisiana as nonresidents. Our veteran tax benefits overview covers the federal side.

Part-year, nonresident and moving to Florida

Domicile drives the residency rules. A resident reports everything, wherever earned. A part-year or nonresident filer reports Louisiana income only, using Form IT-540B.

Louisiana borders Texas, Arkansas and Mississippi. If you live in one of those states and work in Louisiana, you may need a Louisiana nonresident return. If you live in Louisiana and work across the line, you report that income on your resident return and claim the credit for tax paid there. Our remote worker guide walks through the order of filing.

Moving to Florida? Your last Louisiana year is likely a part-year return. See our moving to Florida guide for how to show that your domicile changed.

Estimated tax and paperwork

The Department has a Declaration of Estimated Income Taxes resource for people who do not have enough tax withheld. Look there for the current form and dates. The IRS says sole proprietors, partners and S corporation shareholders generally must make federal estimated payments if they expect to owe when they file.

Gather these before you start.

W-2 and 1099 forms with the Louisiana withholding shown.
A copy of any other state's return if you claim the credit for tax paid there.
School expense receipts, if you plan to use that deduction.
Military orders or duty station records, if you make the residency election.

Louisiana mistakes that cost time

Planning around April 15. The Louisiana date for calendar-year filers is May 15.
Looking for an extension form. None is needed for the automatic extension.
Skipping the payment. The extension gives no extra time to pay.
Using the wrong return. Part-year and nonresident filers use IT-540B, not IT-540.
Using old tax tables. The flat rate applies to tax years 2025 and beyond.
Forgetting the other-state credit support. Keep that state's return.
Ignoring the military election. It can change which state taxes your pay.

When a refund looks late, check status on LaTAP first.

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FAQ

When is a Louisiana income tax return due?

The Department of Revenue says individual returns are due by May 15 for calendar-year filers. Fiscal-year returns are due on the 15th day of the fifth month after the year ends.

Do I have to file a form to extend my Louisiana return?

No. The state gives an automatic six-month extension to file, and no paper or electronic form is needed. It does not extend the time to pay.

Which Louisiana form do I use?

Residents use Form IT-540 and report all income. Nonresidents and part-year residents use Form IT-540B and report only Louisiana-source income.

Is Louisiana's income tax flat or graduated?

For tax years 2025 and beyond, the Department says Louisiana uses a flat rate, replacing the old graduated structure. Check the current instructions for the rate.

Can military spouses choose where they pay tax?

For tax years beginning January 1, 2023 or later, military personnel and spouses can each elect their residence, their spouse's residence, or the service member's permanent duty station.

Sources

General information, not tax advice for your specific situation. Rules can change, so check the official sources below. Zero Fuss Taxes is a PTIN-holding tax preparation firm. We are not a CPA firm, enrolled agents or attorneys.

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Zero Fuss Taxes is a PTIN-holding tax preparation firm. We are not a CPA firm, enrolled agents or attorneys.