Posey County is Indiana's southwestern corner — Mount Vernon along the Ohio River, New Harmony with its 19th-century utopian-community heritage, Poseyville and the smaller towns spread across the agricultural townships. The local property tax base is a quiet mix of small-city residential clustered around Mount Vernon, river-economy commercial and industrial along the Ohio, an active agricultural belt through the central and northern townships, and a meaningful petrochemical-and-energy concentration that gives the county a different industrial profile than the more diversified manufacturing counties to the east.
The 2026 Form 11 notices arrive in mid-April against the same statewide DLGF cost-table reset pushing AVs upward across Indiana. The appeal deadline is June 15, 2026, or 45 days from the mailing date — whichever is later.
Posey County Treasurer's Office: in Mount Vernon. Tax bills are mailed in early April. The Spring Installment is due Monday, May 11, 2026 and the Fall Installment is due Tuesday, November 10, 2026. The 2026 Posey County Budget Order issued January 15, 2026 — meaning tax rates are now locked in for the spring bill.
What's Driving 2026 Posey County AVs
Three local dynamics shape the cycle.
The DLGF Cost-Table Reset
The statewide cost-table update — the same one driving the 12% statewide AV growth in the prior cycle — affects every county. Mount Vernon and Poseyville's residential housing stock will see across-the-board improvement-value movement, with the largest percentage swings on older properties.
The Petrochemical and Industrial Belt
The Ohio River corridor through Posey County hosts a meaningful concentration of petrochemical, fertilizer, and energy-related industrial real estate. These properties involve specialized cost schedules, machinery and equipment considerations, and often (where applicable) abatement schedules that phase in or phase out over multi-year horizons. Owners of C&I parcels along the corridor should review the AV change carefully and compare it against the property's actual operating economics.
Active Farmland
Outside Mount Vernon and the smaller towns, Posey County is meaningful farm country. The 2026 farmland base rate is $2,120 per acre — unchanged from 2025 — but parcel AVs still move based on productivity, soil composition, and influence factors. Posey's flat, river-bottom soils support some of the higher-productivity farmland in southern Indiana.
What to Check on Your Posey County Form 11
The general Form 11 walkthrough applies. Posey-specific items:
Property Class Code
Verify Line 5. The class code determines your cap tier: 1% homestead, 2% other residential and farmland, 3% commercial.
Homestead and SB 1 Credit
If you bought in 2025, verify Form HC-10 was filed. Without it, you lose the homestead deduction, the supplemental homestead deduction (now 40% in 2026), and the SB 1 $300 credit on the spring 2026 bill.
Improvement Value on Older Stock
Mount Vernon and New Harmony both have meaningful historic and pre-1970 housing stock. Documented condition issues are appeal-worthy evidence.
Industrial Personal Property
The business personal property exemption rises to $1M in 2026 (and $2M in 2027) under SB 1. Smaller industrial and commercial operators along the river corridor should verify they're getting the new threshold applied correctly via Form 104.
Posey County Tax Rate Context
Posey County's combined tax rates run modestly below the statewide median, with the industrial tax base along the river absorbing meaningful levy that would otherwise fall on residential.
For appeal economics: a $10,000 AV reduction translates to roughly $150–$220 of annual tax savings for non-cap-bound parcels.
The Mount Vernon, New Harmony, Poseyville Picture
| Area | Character | 2026 considerations |
|---|---|---|
| Mount Vernon (city) | County seat, dense SFR, downtown, river-adjacent | Cost-table moves on older improvements |
| New Harmony | Historic community, tourism, residential | Specialized historic-property considerations |
| Poseyville | Small town, residential | Modest moves; cost-table-driven |
| River corridor | Petrochemical, fertilizer, energy industrial | Specialized C&I valuations |
| Rural townships | High-productivity farmland | Farmland base rate drives Ag AV |
SB 1 and the 2026 Spring Bill
The reform package signed in 2025 takes effect on the spring 2026 tax bill (due May 11):
- 10% supplemental homestead credit, capped at $300 per qualifying homestead.
- Supplemental homestead deduction increases from 35% to 40% of eligible AV.
- Business personal property exemption rises to $1M in 2026 (and $2M in 2027).
Walkthrough in the SB 1 explainer.
Posey County Appeal Logistics
Form 130 is filed with the Posey County Assessor's Office at the Mount Vernon courthouse. Hand-delivery and mail are both accepted; appeals are time-stamped on receipt, not postmark.
Include with your filing:
- Completed Form 130 (one per parcel)
- Stated grounds: market value, error, or uniformity
- 3–5 comparable sales within the same neighborhood code
- Photos for condition-based arguments
- For income property: rent roll and operating statement
- For industrial property: operating data, machinery and equipment schedule, abatement documentation if applicable
PTABOA acknowledges within 30 days. Settlement offers commonly arrive 60–90 days after filing if written evidence supports a reduction. Post-decision, the Indiana Board of Tax Review is the escalation within 30 days.
The Industrial Tax Base and Residential Owners
The petrochemical and energy concentration along the river is the largest single contributor to Posey's commercial/industrial tax base. For residential owners, this means levy is spread over a larger non-residential base than in pure-residential counties — keeping residential rates lower than they would be otherwise. The flip side is that any major industrial closure or large abatement expansion shifts levy back onto residential and small commercial. This is worth keeping in mind when reading multi-year tax rate trends.
High-Productivity Farmland Considerations
Posey County's river-bottom soils are among Indiana's most productive. For active-farming owners, this means the productivity factors that translate the base rate into per-parcel AV are toward the upper end of the state's range. Owners should pull the productivity ratings on their parcel's record card and verify against current soil-survey data — particularly for parcels where drainage improvements or erosion changes might have shifted the underlying soil composition since the last survey.
Decide Early
The optimal Posey County filing window is late April through late May: Form 11 in hand, well before the June deadline, and time to pull supporting documents.
If you'd rather not assemble the package, Property Lookup compares your parcel to recent sales, and Tax Appeal Automation builds the Form 130 evidence file on contingency.
Find Your Posey County Property
- Posey County overview
- Posey residential parcel data
- Posey commercial parcel data
- Posey industrial parcel data
- Posey agricultural parcel data