Ohio’s SD 100 is the annual school district income tax return you file if you lived in one of the state’s taxing school districts during the year. It’s filed alongside your Ohio IT 1040, it’s due April 15, and the tax is calculated using either a traditional income base or an earned income base, depending on what voters in your district approved. Rates run from 0.25% to 2.0%.
Find Your District Number and Tax Base First
Every taxing school district has a four-digit number, and you need yours before you can fill in a single line. The fastest way to get it is “The Finder,” the Ohio Department of Taxation’s lookup tool, which takes a street address or zip code.1Ohio Department of Taxation. The Finder – School District Income Tax The Finder also tells you two things that drive the rest of the return: your district’s tax rate and whether it uses the traditional or earned income base. Your district number also appears on your property tax records and in Box 20 of your W-2.
Which base your district uses determines what gets taxed:
- Traditional base: Tax applies to the same adjusted gross income you report on your Ohio IT 1040, which includes wages, interest, dividends, capital gains, and retirement income. You subtract the personal exemption amount from IT 1040, line 4.2Ohio Department of Taxation. School District Income Tax
- Earned income base: Tax applies only to wages, salaries, tips, and net self-employment earnings. Retirement income, investment gains, interest, and dividends are excluded. No personal exemption deduction applies.3Ohio Department of Taxation. Local School Income Taxes in Ohio
Who Has to File
You need to file the SD 100 if you lived in a taxing school district at any point during the tax year, received income while you were a resident, and have a tax liability on line 8 of the return.2Ohio Department of Taxation. School District Income Tax Ohio defines a resident as someone domiciled in the district, or who lives in and maintains a permanent home there, during all or part of the year.4Ohio Legislative Service Commission. Ohio Code 5748.01 – School District Income Tax Definitions
One trap: if you owe school district tax, you also have to file an IT 1040, even if you’d otherwise be exempt from state filing requirements.5Ohio Department of Taxation. Who Must File Taxes in Ohio The two returns are linked, and the SD 100 pulls figures directly from the state return.
Married couples use the same filing status as on the federal return. Filed jointly for federal? File a joint IT 1040 and a joint SD 100. If you moved during the year and lived in more than one taxing district, you file one SD 100 with a separate schedule for each district, allocating income by your dates of residency.
Filling Out the Return
Download the current-year SD 100 from the Department of Taxation’s forms page or complete it through the state’s online portal.6Ohio Department of Taxation. Tax Forms Have your completed Ohio IT 1040 and all W-2s in front of you before you start. Nearly every figure on the SD 100 comes from one of those documents.
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Enter your Social Security number (and your spouse’s for a joint return), your name, and your current address. Then enter the four-digit school district number. A wrong number sends your payment to the wrong district and takes real work to unwind.
Traditional Base Districts
Start with your Ohio adjusted gross income from the IT 1040. Subtract the personal exemption amount from IT 1040, line 4, to get school district taxable income. Multiply by your district’s rate, listed in the SD 100 instructions and on The Finder, to get your tax liability before credits and payments.
Earned Income Base Districts
Total your qualifying wages, salaries, tips, and net self-employment income. No exemption deduction applies. Multiply by your district’s rate. Retirees in earned income districts often owe nothing if all of their income comes from pensions and investments.
Withholding, Credits, and Balance Due
Check your W-2s for school district tax already withheld, usually shown in Box 19. Enter the total in the payments section, along with any estimated payments made during the year. If payments exceed liability, you have a refund. If liability exceeds payments, that difference is what you owe.
Sign and date the return. Both spouses must sign a joint return. An unsigned SD 100 is treated as unfiled.
Deadline and Extension
The SD 100 is due April 15, the same day as your Ohio IT 1040.7Ohio Department of Taxation. Ohio Department of Taxation If you need more time, Ohio grants an automatic extension to October 15 for both returns.8Ohio Department of Taxation. Ohio’s Individual and School District Income Tax Filing Extension No separate extension form is needed; Ohio honors a federal extension or simply allows the extra time.
The extension gives you more time to file, not to pay. Interest on any unpaid balance starts accruing April 15 regardless. If you expect to owe, estimate the amount and send it in with the Ohio Universal Payment Coupon by the original deadline.
How to Submit the Return
Online Through OH|TAX
The state’s online portal, OH|TAX at tax.ohio.gov, walks you through the SD 100, generates a confirmation, and lets you pay in the same session.7Ohio Department of Taxation. Ohio Department of Taxation Online filing is faster and reduces the math errors that trigger notices.
Paper by Mail
If you file on paper, the mailing address depends on whether you’re enclosing a payment, and returns with payments go to a different processing center than returns without. The current addresses are in the SD 100 instruction booklet; check the current-year version rather than reusing last year’s envelope.
Payment Options
When you owe, Ohio accepts several payment methods:
- Electronic check (ACH): Pay directly from a checking or savings account through OH|TAX. No fee.9Ohio Department of Taxation. Make and Schedule Payments
- Credit or debit card: Visa, Mastercard, Discover, and American Express. The processor charges a convenience fee of 2.65% of the payment, with a $1 minimum.9Ohio Department of Taxation. Make and Schedule Payments
- Check or money order by mail: Payable to “School District Income Tax.” Write the tax year, the last four digits of your Social Security number, and your school district number on the memo line. Include Form SD 40P, the payment voucher.10Ohio Department of Taxation. Ohio SD 40P – School District Income Tax Payment Voucher
Don’t use the IT 40P voucher for school district payments. That form is only for state income tax.11Ohio Department of Taxation. Ohio IT 40P – Original Income Tax Payment Voucher
Estimated Payments and the Underpayment Penalty
If your employer withholds school district tax, you probably don’t need to think about estimated payments. If you’re self-employed, have significant investment income in a traditional-base district, or your withholding is simply too low, make quarterly estimated payments to avoid an interest penalty.12Ohio Department of Taxation. Estimated Payments Use the Ohio Universal Payment Coupon by check, or pay electronically through OH|TAX. Quarterly due dates follow the federal estimated schedule.
You won’t face the underpayment penalty if any of the following is true: your tax liability minus employer withholding is $500 or less, your total payments equal at least 90% of the current year’s liability, or your payments equal at least 100% of last year’s liability as shown on a timely filed prior-year return.13Ohio Department of Taxation. Estimated Income/School District Taxes and the 2210 Interest Penalty When you do owe the penalty, Ohio calculates it on Form IT/SD 2210, quarter by quarter: each late installment accrues interest from its due date until paid or the return’s due date, whichever is later.
Claiming a Refund
If your withholding and estimated payments exceed your liability, claim the overpayment as a refund on the SD 100. Ohio won’t send it automatically just because your employer over-withheld; you have to file the return.14Ohio Department of Taxation. Ohio Individual and School District Income Tax Refunds You have four years from the return’s original due date, not the extended due date, to claim a refund. After that, the money is forfeited.
School District Tax on Your Federal Return
School district income tax counts as a state and local income tax for federal purposes. If you itemize on Schedule A of your federal Form 1040, you can include the school district tax paid during the year in your state and local tax (SALT) deduction.15Internal Revenue Service. Topic No. 503, Deductible Taxes For tax year 2026, the SALT deduction is capped at $40,400 ($20,200 for married filing separately), with the cap phasing down for taxpayers with modified adjusted gross income above $505,000. That single cap covers all state and local income and property taxes combined, so school district tax shares the ceiling with everything else.