Sullivan County sits in west-central Indiana along the Wabash River — Sullivan as the county seat, Carlisle and Farmersburg as smaller communities, the Hoosier Energy Merom Generating Station and its surrounding industrial footprint, and a long coal-mining history that still shapes the county's industrial assessment base. The 2026 cycle plays out here against three distinct submarkets: residential, agricultural, and the heavy-industrial complex that carries a disproportionate share of the county's certified net AV.
Form 11 notices reach Sullivan County mailboxes in the spring, with the spring tax installment due May 10 and the fall installment due November 10. The appeal window — June 15, 2026, or 45 days after the Form 11 mailing date — is the only real opportunity to push back on AV before the rate side locks for the year.
Sullivan County 2026 calendar. Form 11 notices typically mail in the spring. Spring tax due May 10, 2026; fall installment due November 10, 2026. Form 130 appeal deadline: June 15, 2026, or 45 days after the Form 11 mailing date.
Sullivan County's Submarkets
1. Sullivan (City of)
The county seat. Standard small-city residential plus the commercial corridor on US-41. City-of-Sullivan combined rates run above the rural-township average due to municipal services and school district overlay.
2. Coal-Mining and Industrial Parcels
The Merom Generating Station, surface-mined and reclaimed land, and the supporting industrial footprint carry a different valuation story from residential parcels. The statewide DLGF cost-table reset hit C&I and industrial classes hard, and large industrial parcels in particular saw substantial cost-approach AV increases. For industrial owners, the 2026 Form 11 deserves a careful comparison against income-approach evidence.
The coal industry's transition adds another layer. Mined-out and reclaimed land that's no longer producing carries a different valuation than active mining acreage. If the assessor's record hasn't tracked the operational status update, the AV may overstate value.
3. Rural and Agricultural
The bulk of Sullivan County's land area is agricultural. Farmland base-rate movement — set statewide by the DLGF — drives the AV here. Sullivan County's mix of bottomland tillable, upland tillable, woods, and reclaimed surface-mine land means the per-acre breakdown is more nuanced than in a uniformly tillable county.
What to Verify on a Sullivan County Form 11
The statewide Form 11 walkthrough covers the basics. Sullivan-specific items:
Industrial Class and Approach
For industrial parcels, the 2026 cost-approach AV may exceed what income-approach evidence supports. Income evidence (lease rolls, operating statements, capitalization rate analysis) is admissible at PTABOA and frequently produces lower AVs than the cost approach for older industrial assets.
Reclaimed-Land Use Status
Land that was surface-mined and has since been reclaimed should carry a use designation matching current condition — agricultural, forestland, or other classification — not the active-mining classification it carried during operations. A stale designation produces a stale AV.
Wabash River Frontage and Floodplain
Wabash-front parcels carry land coefficients reflecting frontage and floodplain status. A coefficient that fell off in error inflates the land AV.
Homestead Status on 2025 Closings
Confirm with the Sullivan County Auditor that any 2025 closing posted a homestead deduction and the SB 1 $300 homestead credit before the 2026 roll closed.
Acreage Breakdown on Mixed-Use Parcels
The split between tillable, woods, residential homesite, reclaimed land, and outbuildings determines per-acre rate application. Sullivan County parcels with reclaimed acreage are particularly prone to acreage-breakdown drift.
Sullivan County By the Numbers
| Metric | Sullivan County |
|---|---|
| County seat | Sullivan |
| Approximate population | ~20,000 |
| Townships | 9 |
| Notable industrial | Merom Generating Station, coal-mining footprint |
| Spring tax due | May 10, 2026 |
| Fall tax due | November 10, 2026 |
Filing a Sullivan County Form 130
The Sullivan County Assessor's office in Sullivan accepts Form 130 petitions. Practical filing notes:
- One Form 130 per parcel.
- For industrial parcels, lead with income-approach evidence. Rent roll, operating statement, capitalization rate support. Cost-approach assertions alone rarely move PTABOA on a complex industrial asset.
- For reclaimed-land parcels, attach use-status documentation. Reclamation completion records, current-use photos.
- For residential parcels, comparable sales from the same neighborhood code carry the most weight.
- Hand-deliver or certified mail near the deadline. Postmark does not control receipt.
- Track acknowledgment within 30 days.
- Pay during pendency. Indiana law requires payment of the prior year's tax × current rate while a petition is open.
Full process detail in the statewide appeal guide.
SB 1 Homestead Credit on Sullivan County Bills
The 10% / $300 supplemental homestead credit is the new spring 2026 line item for properly-filed homesteads. A representative city-of-Sullivan homestead:
- AV ~$110K, homestead deductions applied
- Post-cap bill ~$1,000
- 10% credit: $100
- Final spring + fall obligation: ~$900 split across two installments
The 2026 business personal property exemption ($1M for 2026, $2M for 2027) also affects Sullivan County's industrial and commercial owners — small businesses that previously filed personal property returns may no longer need to.
When to Appeal in Sullivan County
Strong Sullivan County appeal candidates:
- Industrial parcels with cost-approach AVs above income-approach support.
- Reclaimed-land parcels with stale use designations.
- Wabash-front parcels with floodplain coefficient changes.
- Older Sullivan housing stock with documented condition deficiencies.
- Rural acreage breakdown errors misallocating tillable, woods, and residential.
- Clerical errors on residential parcels — square footage, bedroom count, class code, homestead status.
Property Lookup shows the comparable-sales and parcel context for any Sullivan County property. Tax Appeal builds the petition package on contingency.
Find Your Sullivan County Property
- Sullivan County overview
- Sullivan residential parcel data
- Sullivan agricultural parcel data
- Sullivan industrial parcel data
- Sullivan commercial parcel data