How to Fill Out Form IT-540B: Louisiana Nonresident Income Tax Return

To fill out Louisiana Form IT-540B, start from your completed federal return, use the NPR Worksheet to separate your Louisiana-source income from your total income, apply the resulting Louisiana income ratio to tax calculated at the state’s flat 3% rate, then subtract credits and withholding to find what you owe or are owed. The 2025 return is due May 15, 2026.¹

Who Files IT-540B

IT-540B is the return for nonresidents and part-year residents who had Louisiana-source income and are required to file a federal return.² A nonresident lived outside Louisiana the entire year but earned money tied to the state (wages from work performed there, rental income from Louisiana property, business profits, or gains from Louisiana property). A part-year resident moved into or out of Louisiana during the year. You count as a Louisiana resident if you’re domiciled there, keep a permanent home there, or spend more than six months of the tax year in the state.³

If wages are your only Louisiana income and you worked in the state 30 days or fewer during the calendar year, no withholding is required and you generally have no filing obligation. Cross 30 days and every Louisiana wage dollar becomes taxable, including pay from the first 30 days.⁴ The day count doesn’t apply to other income types: rent, business profits, or capital gains from Louisiana property trigger a filing requirement regardless of how many days you spent there.

Two boundaries worth knowing. Louisiana has no reciprocal tax agreements with any other state, so living in Texas or Mississippi does not shield wages earned across the state line. And if you’re the spouse of an active-duty service member stationed in Louisiana under orders, and you’re only there to be with them while you both keep a legal home elsewhere, your wages are exempt under the Military Spouses Residency Relief Act; you claim it by filing Form L-4E with your employer and revoking it within 10 days if you no longer qualify.⁵

What to Have in Front of You

Pull these together before you open the form:

Your completed federal Form 1040. IT-540B starts from your federal adjusted gross income, and your filing status must match the federal return exactly.⁶
W-2s and 1099s that show Louisiana in the state field or list Louisiana tax withheld.
Exact move-in or move-out dates, if you’re a part-year resident. They determine what belongs in the Louisiana column of the NPR Worksheet.
Social Security numbers for you, your spouse, and any dependents.
Any forms required to support credits you plan to claim (for example, Form R-10610 for the inventory tax credit or Form R-10615 for the school readiness credit).⁷

Completing the Return

Step 1: The NPR Worksheet

The Nonresident and Part-Year Resident Worksheet is where the return really happens. It has two columns, Federal and Louisiana. In the Federal column you list every category of income from your 1040. In the Louisiana column you list only the amounts tied to Louisiana sources: wages for work performed in the state, rental income from Louisiana property, income from a Louisiana business, and, for part-year residents, any income received while you were a resident.⁸

Step 2: Transfer the Two Totals and Compute the Ratio

From the worksheet, carry your federal adjusted gross income to Line 7 and your Louisiana adjusted gross income to Line 8. Divide Line 8 by Line 7 to get your Louisiana income ratio on Line 9. Take the percentage to two decimal places and don’t round up: 48.326% is entered as 48.32%. If your Louisiana income equals or exceeds your federal income, cap the ratio at 100%.⁶

Step 3: Apply the Standard Deduction and 3% Rate

For tax years beginning in 2025, Louisiana taxes individual income at a flat 3%, replacing the old graduated brackets under Act 11 of the 2024 Third Extraordinary Session.⁹ The 2025 standard deduction is $12,500 for single filers and married filing separately, and $25,000 for married filing jointly, qualifying surviving spouse, or head of household. The amounts adjust for inflation starting January 1, 2026.¹⁰

Compute tax as though your full income were Louisiana income, then multiply by your Line 9 ratio. That result is your Louisiana tax before credits.

Step 4: Work Through the Credit Schedules

IT-540B has separate schedules for different categories of credits:

Schedule C-NR for nonrefundable priority 1 credits, including the credit for income taxes paid to other states on the same income.
Schedule F-NR for refundable priority 2 credits, including the Louisiana child care credit. Part-year filers can only count expenses paid while they were Louisiana residents.
Schedule J-NR for nonrefundable priority 3 credits, including the inventory tax credit for taxes paid to Louisiana localities on business inventory.
Schedule I-NR for refundable priority 4 credits.⁷

Each credit has its own eligibility rules and, in most cases, a required attachment. The school readiness credit for child care staff and directors, for example, requires Form R-10615 and the facility’s license number. Missing attachments are a common reason returns stall in processing, so before you file, walk through the instructions once more and confirm every “attach” instruction is satisfied.⁷

Step 5: Subtract Withholding and Finish

Subtract Louisiana withholding from your W-2s and 1099s, along with any estimated payments and refundable credits, to get your final balance due or refund.

How to File

You can file electronically through LaTAP (Louisiana Taxpayer Access Point) or through commercial software that supports Louisiana nonresident returns. Nonresident professional athletes must file electronically. If you file on paper, the address depends on whether you’re paying:⁶

With payment: Department of Revenue, P.O. Box 3550, Baton Rouge, LA 70821-3550.
Refund or no balance due: Department of Revenue, P.O. Box 3440, Baton Rouge, LA 70821-3440.

Make any check or money order payable to the Louisiana Department of Revenue.

Deadline, Extension, and Penalties

The 2025 return is due May 15, 2026, a month after the federal deadline, so your 1040 will typically be finished first.¹ Louisiana grants an automatic six-month extension to file with no form required.² The extension only covers filing, not paying. Interest and a late-payment penalty accrue on any balance still outstanding after May 15.

The late-filing penalty starts at 5% of the unpaid tax and adds another 5% every 30 days, up to 25%.¹¹ If you expect to owe, estimate the amount and send a payment by May 15 even if the return itself isn’t ready.

Checking Your Refund

Once the return is in, use the Where’s My Refund? tool on the Department of Revenue site, or log into LaTAP. You’ll need your Social Security number, filing status, and the exact refund amount from the return.¹² Electronic returns generally clear in several weeks; paper returns take longer.

1
Louisiana Department of Revenue. Individual Income
2
Louisiana Department of Revenue. Individual Income Tax
3
Justia. Louisiana Revised Statutes Title 47 RS 47-31 – Individuals, Corporations, and Trusts Subject to Tax
4
Ernst & Young. Louisiana Regulations Adopt Expansion of Nonresident Income Tax and Withholding Exemption to 30 Days
5
Louisiana Department of Revenue. Exemption from Withholding Louisiana Income Tax Form L-4E
6
Louisiana Department of Revenue. 2025 Louisiana Nonresident and Part-Year Resident IT-540B
7
Louisiana Department of Revenue. Louisiana Form IT-540B Instructions
8
Louisiana Department of Revenue. Instructions for Nonresident and Part-Year Resident NPR Worksheet
9
Louisiana Department of Revenue. Revenue Information Bulletin No. 25-012 – Louisiana Individual Income Tax Reform
10
Louisiana Department of Revenue. Are There Any Changes to the Combined Personal Exemption Standard Deduction
11
Louisiana Department of Revenue. Penalties
12
Louisiana Department of Revenue. Where’s My Refund?