The October 15 Tax Extension Deadline: America's Tax Complexity Map

October 15 is the finish line for taxpayers who requested an extension this year. It's the date circled on calendars, the deadline tax preparers build their fall schedules around, and, for many filers, the last real opportunity to get a complicated return right instead of rushed.

Not every return takes the same amount of work. A taxpayer with a single W-2 may have a relatively straightforward return. Someone with business income, investment gains, rental property, or a pass-through business interest is working with more moving parts — more forms and documentation.

That raises a natural question: where in the country are those more involved financial situations most common? To find out, FileTax.com analyzed IRS Statistics of Income data across all 50 states, looking at six financial indicators associated with more involved tax reporting or preparation: business income, capital gains, partnership and S-corp income, rental and royalty income, itemized deductions, and qualified dividends. Rather than looking at dollar amounts, the analysis measured how many returns in each state reported each of these items, relative to the state's total returns — a truer measure of how common these financial situations are, regardless of a state's size.

We combined those six measures into a single Tax Complexity Score for each state and ranked the states accordingly, from Colorado at #1 to West Virginia at #50. The result is a state-by-state look at where these financial characteristics appear most — and least — often across the country.

A note on what this study does and doesn't show: the Tax Complexity Score reflects how prevalent these six financial characteristics are in a state's tax returns. It is not a measure of tax rates, overall tax burden, or how many taxpayers actually filed for an extension. October 15 is simply the timely hook for the research — not a claim that any of these factors caused taxpayers to seek more time.

National Highlights

#1 Highest Tax Complexity Score: Colorado — 85.33

Lowest Tax Complexity Score: West Virginia — 15.33

Most Common Primary Drivers: Business Income is the most common sole Primary Driver, leading 13 states. Rental/Royalty Income is the sole Primary Driver in 11 states, while Qualified Dividends is the sole Primary Driver in eight. Montana and Massachusetts each have two indicators tied as Primary Drivers.

Notable Finding: The West and Northeast dominate the top of the rankings — nine of the top 10 states come from those two regions, with Virginia as the only state from outside them to crack the top 10. Colorado's #1 ranking isn't driven by a single standout metric; all six indicators are at or above the 76th percentile, giving it an unusually broad, high-ranking profile across the six indicators.

National Findings

The Rocky Mountain divide.

Colorado and New Mexico sit at opposite ends of the map. Colorado's #1 ranking and New Mexico's tie for #48 make them the starkest neighbor contrast in the study. Both are Western states, but Colorado's broad strength across all six indicators is essentially the inverse of New Mexico's profile, where every measure except rental/royalty income ranks in the bottom half nationally. Geography alone doesn't predict complexity — the underlying financial mix does.

Two neighboring Appalachian states sit at the bottom of the rankings.

Kentucky and West Virginia are among the three lowest-scoring states in the country, according to the study. West Virginia (#50) and Kentucky (tied for #48) both show most of their six indicators clustered near the bottom nationally, rather than being dragged down by one weak measure.

Virginia stands apart from the rest of the South.

The South's average score (41.67) trails every other region, but Virginia ties for #7 nationally, more than 26 points above its own region's average — and still well ahead of its next-closest Southern peers, Florida (#15) and Maryland (#18). Its strength in itemized deductions, capital gains, and qualified dividends shares several of the investment- and deduction-related strengths seen among higher-ranking Northeastern states.

Rental and royalty income creates a notable cluster across the Great Plains.

North Dakota, South Dakota, Iowa, and Kansas (Midwest) are joined by Oklahoma (South) in having Rental/Royalty Income as their Primary Driver — five states linked by the same Primary Driver despite spanning two regions and ranking from #17 to #29 nationally. The pattern creates a notable geographic cluster across the central U.S.

Business Income is the country's most common Primary Driver, but it rarely produces a top-tier score.

Business Income is the most common Primary Driver, but it rarely translates into a high overall ranking. Of the 13 states it leads, only three rank in the top half nationally: New York (#7), Florida (#15), and North Carolina (#25). Georgia has the country's highest Business Income prevalence but ranks #27 overall, showing how much the final score depends on performance across all six indicators.

Each of the six indicators has a different national leader.

No single state dominates across the board.

• Business Income: Georgia (#27 overall)
• Capital Gains: Washington (#7 overall)
• Partnership/S-Corp Income: Utah (#21 overall)
• Rental/Royalty Income: North Dakota (#24 overall)
• Itemized Deductions: Maryland (#18 overall)
• Qualified Dividends: Connecticut (#6 overall)

Colorado tops the national rankings without leading any single indicator, while Georgia (#27), Utah (#21), and Maryland (#18) each lead an individual category without reaching the top 15 overall. Washington (#7) and Connecticut (#6) come closest to turning category leadership into a top-tier overall ranking. Together, the results show why the Tax Complexity Score rewards strength across multiple indicators rather than dominance in just one.

Regional Findings

Northeast

The Northeast posts the highest average Tax Complexity Score of any region (60.07), with investment-related indicators playing a prominent role among its higher-ranking states. New Jersey, Massachusetts, and Connecticut — the region's top three — are all led by Qualified Dividends or Capital Gains, and the pattern holds further down the list: Vermont and New Hampshire are also Qualified Dividends states. Together, these results show the prominence of investment-related indicators among several of the Northeast’s higher-ranking states.

Midwest

The Midwest's average score (47.67) is modest, but its two leaders, Minnesota (#11) and Illinois (#13), reach the top of the region a different way than their Great Plains neighbors — through capital gains, partnership/S-corp income, and qualified dividends rather than rental and royalty income. That split gives the Midwest two distinct regional stories: an investment- and business-income-driven cluster among its upper-Midwest leaders, and a property-income-driven cluster across the Dakotas, Iowa, and Kansas.

South

The South has the lowest average score of any region (41.67), and Business Income is by far its most recurring Primary Driver — it leads Florida, Georgia, Louisiana, Texas, Tennessee, Alabama, Mississippi, Kentucky, and South Carolina alike. Virginia is the exception: it's the only Southern state to crack the national top 10, tying for #7 with a profile led by Itemized Deductions rather than Business Income, which is why it stands apart from many of the lower-ranking states in the region.

West

The West's average score (59.28) is nearly as high as the Northeast's. Colorado tops the entire country through broad strength across all six indicators, while Washington leads the nation outright in Capital Gains and Oregon cracks the top 10 largely on Itemized Deductions. The West’s higher-ranking states reach their scores through a mix of different leading indicators.

Methodology

FileTax.com's Tax Complexity Score is based on the state-total records from the IRS 2022 Statistics of Income (SOI) ZIP Code dataset. The analysis uses the state-level totals provided in the dataset rather than aggregating or averaging ZIP-level percentages. It covers all 50 states and excludes D.C.

The study examines six financial characteristics associated with more involved tax reporting or preparation. They include business income, capital gains, partnership or S-corp income, rental/royalty income, itemized deductions, and qualified dividends. For each indicator, we calculated its rate as a share of total returns in each state (the number of returns reporting that item, divided by the state's total returns) rather than using dollar amounts. That keeps the comparison fair across states of very different sizes.

States were then ranked from lowest to highest on each indicator's rate, and each state's position was converted into a Percentile Rank using the formula:

Percentile Rank = (State Position ÷ 50) × 100

where State Position is the state's rank on that indicator, from 1 (lowest rate) to 50 (highest rate). The highest-ranking state on each indicator receives a Percentile Rank of 100.

The six Percentile Ranks were averaged, with each indicator weighted equally, to produce a state's Tax Complexity Score. States were ranked nationally from highest to lowest based on that score to determine National Rank. A state's Primary Driver is the single indicator in which it posted its highest Percentile Rank; when two indicators tied for a state's highest rank, both are listed.

The Tax Complexity Score measures how common these six financial characteristics are on a state's tax returns — not tax rates, overall tax burden, or how many taxpayers actually filed for an extension.