How Oklahoma income tax works: federal AGI, a small deduction, 4.5%

Oklahoma’s income tax is, for practical purposes, 4.5% of federal adjusted gross income after a short list of subtractions, a standard deduction of $6,350 single or $12,700 joint, and $1,000 for each person on the return. The law describes four brackets, 0%, 2.5%, 3.5% and 4.5%, but the top one begins at $7,200 of taxable income on a single return and $14,400 on a joint one, so the lower brackets together are worth about $215 to a single filer and $430 to a couple. Everything above that is 4.5%. There is no local income tax anywhere in the state, no preferential rate for capital gains, and nothing is indexed: the deduction, the exemptions, the bracket lines and every income limit are the same numbers they were last year.

Two facts drive the rest. Form 511 starts at federal AGI, so every deduction taken below the AGI line, including the new federal deductions for tips, overtime, seniors and car-loan interest, never reaches Oklahoma. And Oklahoma makes you follow your federal choice between the standard deduction and itemizing, then rewrites the itemized total with a $17,000 cap.

Who files

A full-year resident files Form 511 when gross income from all sources exceeds the standard deduction plus one exemption: $7,350 single or married filing separately, $10,350 head of household, $14,700 married filing jointly, $13,700 for a qualifying surviving spouse. Part-year residents and nonresidents file Form 511-NR once Oklahoma-source gross income reaches $1,000. Residency, the seven-month presumption and the move-year return are in Moving to Oklahoma.

Where it starts: federal AGI

Line 1 of Form 511 is federal adjusted gross income: income after the Schedule 1 adjustments, an IRA deduction, an HSA deposit, student loan interest, but before the standard deduction and everything beneath it. An above-the-line move cuts Oklahoma tax at 4.5%; a below-the-line deduction does nothing here. A tipped worker who owes no federal tax on $8,000 of tips still owes Oklahoma $360 on them. The $6,000 federal senior deduction, the overtime deduction and the car-loan interest deduction are in the same position. No add-back is needed, because nothing was ever taken out.

The flip side is that Oklahoma incorporates the Internal Revenue Code as amended, so every above-the-line change in the 2025 federal law, bonus depreciation among them, flows straight through to line 1. More in What is new in Oklahoma for 2026.

The subtractions

Schedule 511-A takes income out of federal AGI. The lines that come up are below, with their numbers, because the software asks for them by line and a missed line is tax paid for nothing.

Lines A5 and A6 share one $10,000 per person: a $9,000 state pension and a $12,000 IRA withdrawal subtract $10,000, not $19,000. Each spouse is figured separately.

Retirement income. Social Security, military retirement, CSRS in lieu of Social Security and railroad retirement come off in full. Everything else, government pensions, private pensions, 401(k)s, IRAs and Roth conversions, shares one $10,000 exclusion per person with no age requirement. That split is the subject of Oklahoma for retirees.

The Oklahoma capital gain deduction. Oklahoma taxes capital gains as ordinary income, but Form 561 removes the whole gain on Oklahoma real estate or tangible property owned at least five uninterrupted years, and on an interest in a company headquartered in Oklahoma for three years and owned for two. A farm, a rental house or a family business qualifies; mutual funds and brokerage gains do not. Software routinely leaves the line blank because the federal return never asks where the property was.

The additions and adjustments

Schedule 511-B adds back the few things Oklahoma taxes that the federal return does not: interest on other states’ municipal bonds, a 529 rollover or nonqualified withdrawal that reverses an earlier deduction, and losses from out-of-state property or business. For most people the only one is the municipal bond line.

Schedule 511-C holds Oklahoma-only adjustments that behave like subtractions. Active-duty military pay, including Reserve and National Guard pay, is excluded in full for residents (C1). Contributions to Oklahoma’s own 529 plans are deducted up to $10,000 a year, $20,000 joint, counting deposits made through April 15 of the following year (C3); other states’ plans do not qualify. Foster parents under a child-placing agency contract deduct up to $5,000 (C4).

Form 511 line 4 removes income from property or a business in another state rather than crediting it; out-of-state wages stay in and are relieved by the credit on Form 511-TX.

The deduction and the exemptions

Oklahoma has its own standard deduction and it is small: $6,350 single or married filing separately, $9,350 head of household, $12,700 married filing jointly or qualifying surviving spouse. It has not changed since 2017 and it is not indexed. Then $1,000 each for the taxpayer, spouse and each dependent: $16,700 for a couple with two children, $7,350 for a single filer.

Two extra exemptions exist. Anyone 65 or older gets another $1,000, but only if federal AGI is $15,000 or less single, $25,000 or less joint, $12,500 or less married filing separately or $19,000 or less head of household, and a Roth conversion is excluded from that AGI test. Legal blindness earns $1,000 with no income limit.

If you took the standard deduction federally, you take Oklahoma’s standard deduction. If you itemized federally, you must itemize on Schedule 511-D, even when the result is less than $12,700. Schedule 511-D starts from the federal Schedule A total, strips out any state and local income or sales tax, and caps what remains at $17,000, except that charitable gifts and medical expenses sit outside the cap. Mortgage interest, property tax and gambling losses compete for the same $17,000, so the higher federal SALT cap helps only up to that ceiling; a household with $25,000 of mortgage interest and property tax deducts $17,000 here. A large charitable or medical year is the way around the cap.

The rate

Federal AGI, less subtractions, plus additions, less adjustments, is Oklahoma AGI. Oklahoma AGI less the deduction and exemptions is Oklahoma taxable income. The tax comes from the tables in the Form 511 packet, which for 2026 are built on these brackets:

Head of household uses the joint bracket schedule but its own $9,350 standard deduction.

House Bill 2764, signed in May 2025, cut the top rate from 4.75% to 4.5% for 2026, merged the three lowest brackets into the 0% bracket, and wrote a trigger into law. Each December the State Board of Equalization certifies whether state collections for the latest fiscal year beat the prior peak year by at least 125% of the cost of another quarter-point cut, about $340 million for the first test. If they do, the top rate falls another 0.25 point two tax years later, repeating until the rate reaches zero; a declared revenue failure cancels a pending cut. On December 22, 2025 the Board found the test not met, fiscal 2025 collections of $13.54 billion against a fiscal 2023 peak of $14.18 billion, so the rate stays 4.5% for 2027. The next test is December 2026. The accurate version of “Oklahoma is eliminating the income tax” is that the rate is 4.5% this year and next, and the trigger has not fired.

The credits

Nonrefundable credits reduce the tax and stop at zero. The earned income credit and the sales tax relief credit are refundable: if they exceed the tax, the Department pays the difference.

Business credits go on Form 511-CR (line 17) and the $1,000 homeschool credit on Form 591-D (line 29). The Parental Choice Tax Credit for private school tuition is applied for separately and paid by check to the school; it is not a line on Form 511. The family credits are covered in Credits and breaks for Oklahoma families.

Two of these have cliffs rather than phase-outs. The child credit is available at $100,000 of federal AGI and gone at $100,001. The sales tax relief credit stops at $20,000 or $50,000 of gross household income, a figure that counts Social Security and pensions the income tax ignores. It is the credit most often missed, because the people it is for often owe nothing and do not file.

Withholding and estimated payments

Oklahoma withholding on wages is set by Form OK-W-4, where each allowance is worth $1,000, and the Tax Commission’s tables have the standard deduction built in. Pension payers withhold Oklahoma tax on request, and a retiree with a pension above the $10,000 exclusion usually wants them to.

Estimated payments on Form OW-8-ES, or through OkTAP, are required when you expect to owe $500 or more after withholding and your withholding will be less than the smaller of 70% of this year’s tax or 100% of last year’s. Payments are due April 15, June 15, September 15 and January 15. Underpayment interest runs at 20% a year, but none is charged when the tax shown on the return is under $1,000.

How to file

OkTAP, the Tax Commission’s own portal, files Form 511 free for any resident, takes payments and shows refund status. Paper returns are due April 15, 2027. Electronically filed returns get until April 20, 2027, provided any payment due is also made electronically. A federal extension automatically extends the Oklahoma return when no Oklahoma tax is owed; attach a copy. If tax is owed, file Form 504-I with payment by April 15. An extension is to file, not to pay: pay at least 90% of the tax by April 15 to avoid the 5% late-payment penalty, and interest at 1.25% a month runs from April 15 on any balance regardless. More in Oklahoma calendar and forms.