Not all Indiana counties assess property with equal accuracy. Some counties consistently assess properties above market value, while others maintain tight alignment between assessments and actual sale prices. The difference matters — if you live in an over-assessing county, you could be paying more than your fair share in property taxes.
We analyzed assessment equity data across all 92 Indiana counties to identify where the problem is worst.
How We Measure Over-Assessment
Assessment accuracy is measured using metrics established by the International Association of Assessing Officers (IAAO). The key metric is the assessment-to-sale ratio — when a property sells, we compare its assessed value to its sale price.
A ratio of 1.0 means the assessment perfectly matched the sale price. Above 1.0 means over-assessed. Below 1.0 means under-assessed.
But individual ratios aren't enough. We need to look at the distribution of ratios across all sales in a county. The IAAO uses several statistical measures for this:
Coefficient of Dispersion (COD)
The COD measures how consistently properties are assessed relative to each other. A low COD means assessments are uniform — even if they're all slightly high or low, at least everyone is treated equally. A high COD means some properties are over-assessed while others are under-assessed, creating inequity.
The IAAO standard for residential property is a COD below 15. Counties exceeding this threshold have assessment uniformity problems.
Price-Related Differential (PRD)
The PRD measures whether high-value or low-value properties are assessed more accurately. A PRD above 1.03 indicates regressive assessment — lower-value properties are assessed at a higher percentage of market value than higher-value properties. This means lower-income homeowners carry a disproportionate share of the tax burden.
Median Assessment Ratio
The median ratio across all sales tells you whether the county is generally over- or under-assessing. A median above 1.0 means the county is systematically over-assessing. Below 1.0 means under-assessing.
What Over-Assessment Costs You
If your county has a median assessment ratio of 1.10 (10% over-assessed) and you own a home that should be assessed at $200,000, your assessment might be $220,000 instead. At a typical Indiana tax rate of $20 per $1,000 of assessed value, that $20,000 excess assessment costs you $400 per year in additional property taxes.
In counties with higher tax rates, the penalty is even steeper. Indiana property tax rates vary significantly by county, so over-assessment in a high-rate county compounds the damage.
Which Counties Are Affected?
Counties most likely to have over-assessment issues share several characteristics:
Resource Constraints
Smaller counties with limited assessor budgets and staff may not have the resources to conduct thorough reassessments. When assessment offices are understaffed, properties tend to be assessed based on outdated data, leading to inaccuracies in both directions.
Rapid Market Changes
Counties experiencing rapid property value changes — either increases or decreases — are more likely to have assessments that don't reflect current market conditions. If your market has cooled but assessments haven't caught up, you're effectively over-assessed.
Infrequent Reassessments
While Indiana requires annual trending, the thoroughness of the trending process varies by county. Counties that rely heavily on automated trending without ground-truthing against current sales data may drift from market values over time.
Limited Sales Data
Rural counties with few annual sales have less data to calibrate assessments against. Counties like Ohio County (Indiana's smallest, with roughly 3,500 parcels) simply don't have enough transactions to build robust statistical models.
The Equity Problem
Over-assessment isn't just about paying too much — it's about fairness. When a county has a high COD, some homeowners are paying significantly more than their fair share while others pay less. This violates Indiana's constitutional requirement for uniform and equal assessment.
The DLGF (Department of Local Government Finance) monitors assessment equity and can intervene when counties fall below standards. But enforcement is uneven, and many counties operate with equity metrics that the IAAO would flag as problematic.
Our Assessment Equity Audits product provides IAAO-compliant ratio studies for county assessors, helping them identify and correct equity issues before the DLGF gets involved.
What You Can Do
Check Your Assessment
Use AribaTax's Property Lookup to see your current assessed value and compare it against comparable sales in your area. If your assessment exceeds what similar properties are selling for, you likely have grounds for an appeal.
File an Appeal
Indiana's Form 130 appeal process gives every property owner the right to challenge their assessment. The key is having solid comparable sales evidence — and the deadline is 45 days from your assessment notice or June 15, whichever is later.
Our Tax Appeal Automation product handles the entire process: identifying over-assessments, finding comparable sales evidence, generating Form 130 petitions, and tracking the appeal through resolution. We work on contingency — you only pay if your appeal succeeds.
Use AI Valuation
Our AI Valuation product can estimate your property's market value using models trained exclusively on Indiana sales data. If the model says your property is worth less than its assessed value, that's a strong signal you should appeal.
County-Specific Assessment Data
Explore assessment data for specific counties to see how your area performs:
- Marion County — Indiana's largest, with 350,000+ parcels
- Lake County — Complex assessment landscape with diverse property types
- Allen County — Fort Wayne metro with strong CAMA data
- Vanderburgh County — Evansville region
- Delaware County — Muncie area, older housing stock
- Madison County — Anderson region
- Howard County — Kokomo area
For County Assessors
If you're a county assessor reading this, we can help. Our Assessment Equity Audits product delivers IAAO-compliant ratio studies with COD, PRD, and PRB analysis at the county, township, neighborhood, and property class levels. Reports are formatted for DLGF compliance and county council presentations.
Assessment equity isn't just good policy — it's a constitutional requirement. Let data show you where to focus your reassessment efforts.