What is Form SD-100?
Quick answer: Form SD 100 is the separate return you file if you lived, during any part of the year, in one of the more than 200 Ohio school districts that levy their own income tax. It is filed in addition to the Ohio IT 1040. Each taxing district uses one of two tax bases — a “traditional” base (your modified adjusted gross income less exemptions) or an “earned income” base (only your wages and self-employment income) — and each district sets its own rate, which you look up in the Department’s school district rate table or with The Finder at tax.ohio.gov. The return is due April 15, 2026, and a paper return goes to one of two Columbus PO boxes. Below, the Ohio SD 100 instructions are explained one line at a time, including how the two tax bases differ.
Form SD 100 reports the income tax owed to an Ohio school district. Ohio’s school district income tax is separate from both the state income tax and any city income tax: more than 200 school districts have voted to levy it, and only residents of those districts owe it. The SD 100 figures that tax, credits your school district withholding and estimated payments against it, and produces a refund or a balance due — much like the IT 1040 does for the state.
Two things make the SD 100 its own return. First, each district chooses its tax base: a “traditional” district taxes the same income the state does (modified adjusted gross income less exemptions), while an “earned income” district taxes only your wages and self-employment earnings, with no deductions or exemptions. Second, each district sets its own rate. So before you can complete the form you need to know, for every district you lived in during the year, whether it taxes, on which base, and at what rate — all of which are in the Department’s school district rate table and The Finder.
Key Figures — Tax Year 2025 (Ohio SD 100)
- Two tax bases, set by each district: the traditional tax base (SD 100 Line 5 = modified adjusted gross income minus exemptions, apportioned by residency) or the earned income tax base (only wages, salaries, tips, and net self-employment income, with no deductions or exemptions).
- Each taxing school district sets its own rate — check your district’s current rate and tax base with The Finder at tax.ohio.gov/finder or the Department’s school district rate table.
- Line 1 starts from Ohio adjusted gross income (Ohio IT 1040, Line 3); Line 2 adds back the business income deduction; Line 4 is the exemption amount from Ohio IT 1040, Line 4.
- Senior citizen credit: up to $50 per taxing district, for taxpayers 65 or older (Lines 26 and 36).
- Use the Schedule of School District Residency for each district you lived in — enter “9999” for any part of the year you were a nonresident of Ohio; residency factor = days as a resident ÷ 365 (tool at tax.ohio.gov/SDresidency).
- Filing deadline: April 15, 2026, the same as the Ohio IT 1040. A school district liability also requires you to file the IT 1040.
- Mail a paper SD 100 to the Ohio Department of Taxation, Columbus: P.O. Box 182197 (43218-2197) without a payment, or P.O. Box 182389 (43218-2389) with a payment. Mark any OUPC “School District Income Tax.”
Who Must File Ohio Form SD 100?
You must file an SD 100 if you lived in a taxing school district during any part of 2025 and you have a school district income tax liability. A school district liability also means you are required to file the Ohio IT 1040, even if you would otherwise be exempt from filing it.
The Department recommends filing an SD 100 if you were a resident of a taxing school district at any time during the year, even if no tax is due, so the Department has a record and does not send a non-filer notice.
You do not file an SD 100 for a district that does not levy the tax. Living in Ohio is not enough — the district itself must have an income tax. Check with The Finder.
Part-year residents of a taxing district file and use the Schedule of School District Residency to apportion income to the period they lived there.
How to File Ohio Form SD 100
- Electronically: File free through OH|TAX eServices at tax.ohio.gov, or use approved software. The system applies the correct base and rate for your district.
- By mail: Complete the SD 100, the Schedule of School District Residency, the applicable Traditional or Earned Income Tax Base Schedule for each district, and the Schedule of School District Withholding; attach your income statements; and mail it to the correct Columbus address.
- Payment: Pay at tax.ohio.gov/pay, or mail a check with the Ohio Universal Payment Coupon (OUPC) marked “School District Income Tax.” Do not send a check without the OUPC.
Before you start, finish your Ohio IT 1040 (the SD 100 pulls figures from it), and look up each school district you lived in — its four-digit number, whether it taxes, its base, and its rate — with The Finder at tax.ohio.gov/finder.
When Is Ohio Form SD 100 Due?
- Primary deadline: April 15, 2026 for the 2025 tax year, the same date as the Ohio IT 1040.
- Extension: An IRS extension automatically extends the SD 100 filing deadline as well, to the federal extended due date. It does not extend the time to pay.
- Interest and penalties: Interest runs on tax not paid by April 15, 2026, and late-filing and late-payment penalties may apply.
- Estimated payments: If you expect to owe school district tax that withholding will not cover, make estimated payments with Form SD 100ES. Underpayment is figured on Form IT/SD 2210 and reported on Line 9.
Where to Mail Ohio Form SD 100
Send a paper return to the Ohio Department of Taxation in Columbus, at the address that matches your situation. Mark any OUPC “School District Income Tax.”
- Return without a payment: Ohio Department of Taxation, P.O. Box 182197, Columbus, OH 43218-2197
- Return with a payment: Ohio Department of Taxation, P.O. Box 182389, Columbus, OH 43218-2389
The Ohio IT 1040 goes to different PO boxes — do not combine the two returns in one envelope unless the instructions tell you to.
How to Complete Ohio Form SD 100 Line by Line
Top of the form
Filing status: Match your Ohio IT 1040 — single, head of household, or qualifying surviving spouse; married filing jointly; or married filing separately.
Amended return / NOL carryback: Check the amended box and include Ohio SD RE if you are correcting a filed SD 100; check the NOL carryback box and include Schedule IT NOL if you are carrying a net operating loss back.
Schedule of School District Residency
Complete a line for each school district you (and your spouse, if filing jointly) resided in during 2025. Enter the four-digit district number, the dates of residency, your days as a resident, and the residency factor (days as a resident ÷ 365). Enter “9999” as the district number for any part of the year you were a nonresident of Ohio. The Department’s tool at tax.ohio.gov/SDresidency calculates the days and factor for you.
Income and tax base (Lines 1–5)
Line 1: Ohio adjusted gross income. Enter the amount from Ohio IT 1040, Line 3.
Line 2: Business income deduction add-back. Enter the business income deduction from the Ohio Schedule of Adjustments, Line 13. If you did not take that deduction, enter zero.
Line 3: Modified adjusted gross income. Line 1 plus Line 2. If negative, enter zero.
Line 4: Exemption amount. Enter the exemption amount from Ohio IT 1040, Line 4.
Line 5: Modified adjusted gross income less exemptions. Line 3 minus Line 4. If negative, enter zero. This is the starting figure for a traditional tax base district.
Traditional Tax Base Schedule (per district)
Complete this schedule for each traditional-base district you lived in.
- Line 22: The portion of Line 5 you received while a resident of that district. If negative, enter zero.
- Line 23: The lesser of Line 5 or Line 22.
- Line 24: The district’s tax rate, from the rate table or The Finder.
- Line 25: School district tax — Line 23 times Line 24.
- Line 26: Senior citizen credit — up to $50 for this district, if you are 65 or older.
- Line 27: Tax after credits — Line 25 minus Line 26, not below zero.
- Line 28: Add all Line 27 amounts (including any extra copies of the schedule). Enter here and on Line 6.
Earned Income Tax Base Schedule (per district)
Complete this schedule for each earned-income-base district you lived in.
- Line 29: Wages, salaries, tips, and other employee compensation from your federal return received while a resident of that district.
- Line 30: Net self-employment earnings from your federal return received while a resident of that district. Use a minus sign if negative.
- Line 31: Line 29 plus Line 30. If negative, enter zero.
- Line 32: The portion of Line 3 received while a resident of that district. If negative, enter zero.
- Line 33: The lesser of Line 31 or Line 32.
- Line 34: The district’s tax rate.
- Line 35: School district tax — Line 33 times Line 34.
- Line 36: Senior citizen credit — up to $50 for this district, if you are 65 or older.
- Line 37: Tax after credits — Line 35 minus Line 36, not below zero.
- Line 38: Add all Line 37 amounts. Enter here and on Line 7.
Tax, payments, and balance (Lines 6–21)
Line 6: Total tax from traditional tax base districts, from Line 28.
Line 7: Total tax from earned income tax base districts, from Line 38.
Line 8: School district income tax liability after credits — Line 6 plus Line 7.
Line 9: Interest penalty on underpayment of estimated tax, from Form IT/SD 2210.
Line 10: Total school district income tax liability before withholding or estimated payments — Line 8 plus Line 9.
Line 11: School district income tax withheld, from the Schedule of School District Withholding, Part A, Line 1. Attach the schedule and your income statements.
Line 12: Estimated and extension payments, and any credit carried forward from your 2024 return.
Line 13: Total school district income tax payments — Line 11 plus Line 12.
Line 15: Line 13 minus Line 14 (Line 14 is used only on an amended return).
Line 16: Tax due — Line 10 minus Line 15. If Line 15 is negative, add it to Line 10 instead.
Line 17: Interest due on late payment of tax, from the instructions.
Line 18: Total amount due — Line 16 plus Line 17. Pay at tax.ohio.gov/pay or mail a check with the OUPC.
Line 19: Overpayment — Line 15 minus Line 10.
Line 20: On an original return, the part of Line 19 credited toward next year’s school district tax.
Line 21: Refund — Line 19 minus Line 20. If it is $1.00 or less, no refund is issued.
Sign the return
Sign and date under penalty of perjury. Both spouses must sign a joint return.
Common Mistakes to Avoid
- Not filing the SD 100 when you owe school district tax. Withholding by your employer does not replace the return, and a school district liability also forces you to file the IT 1040.
- Assuming you owe because you live in Ohio. Only residents of a district that actually levies the tax owe it — check The Finder.
- Using the wrong tax base. A district is either traditional or earned income — using the wrong one changes your taxable income entirely.
- Guessing the rate. Each district sets its own rate; look it up in the rate table or The Finder.
- Skipping the residency schedule. Part-year residents must apportion income with the Schedule of School District Residency and enter “9999” for out-of-Ohio periods.
- Forgetting the Schedule of School District Withholding. Line 11 withholding is not credited without it and your income statements.
- Mailing to the IT 1040 PO boxes. The SD 100 has its own two Columbus addresses.
- Not marking the OUPC. A mailed payment coupon must say “School District Income Tax.”
Frequently Asked Questions
Do I have to file an SD 100? Yes, if you lived in a taxing school district during the year and owe school district income tax. The Department also recommends filing if you were a resident of a taxing district even when no tax is due.
How do I know if my school district has an income tax? Use The Finder at tax.ohio.gov/finder — it tells you whether your district taxes, which base it uses, and its rate.
What is the difference between the two tax bases? A traditional tax base district taxes your modified adjusted gross income less exemptions. An earned income tax base district taxes only your wages and self-employment income, with no deductions or exemptions.
What is the school district tax rate? It varies — each district sets its own. There is no single statewide rate.
When is the SD 100 due? April 15, 2026 for 2025, the same as the Ohio IT 1040.
Where do I mail it? P.O. Box 182197, Columbus, OH 43218-2197 without a payment, or P.O. Box 182389, Columbus, OH 43218-2389 with a payment.
I moved out of a taxing district mid-year. What do I do? File the SD 100 and use the Schedule of School District Residency to apportion your income to the months you lived in the district.
Is there a senior citizen credit? Yes — up to $50 per taxing district for taxpayers 65 or older.
Final Review Before Filing
- You confirmed with The Finder that your district levies the tax, and its base and rate.
- The Schedule of School District Residency covers every district you lived in, with “9999” for out-of-Ohio periods.
- Lines 1 and 4 match your Ohio IT 1040, Lines 3 and 4.
- The correct base schedule (Traditional or Earned Income) is completed for each district.
- The rate on Line 24 or Line 34 is the district’s current rate.
- Senior citizen credit is claimed only if you are 65 or older, capped at $50 per district.
- The Schedule of School District Withholding and your income statements are attached.
- The return is signed and dated (both spouses if joint).
- A mailed payment includes the OUPC marked “School District Income Tax” and goes to the correct PO box.
Sources & verification
- Issuing agency: Ohio Department of Taxation
- Official documents: Form SD-100 (PDF) · instructions (PDF)
- Checked against: 2025 Ohio SD 100 + 2025 IT 1040/SD 100 instruction booklet
- Last verified: September 9, 2026
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General information from the official form and its instructions, not advice for your circumstances. See the full disclaimer.