TaxProper
Summer 2019AcquiredTaxProper helps large Real Estate owners manage their property taxes.
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TaxProper helps large Real Estate owners manage their property taxes.
Explore the risks and possibilities with a prompt for ChatGPT, Claude, or your agent.
TaxProper was a Chicago-based property tax technology company founded in May 2019 by Thomas Dowling and Geoff Segal through Y Combinator's Summer 2019 batch. The company launched as a consumer-facing tool that automated property tax appeals for homeowners, then executed a deliberate pivot to an enterprise SaaS platform serving institutional real estate operators — managing tax payments, forecasting, and appeals across large portfolios nationwide.
The pivot worked. By the time Opendoor Technologies acquired TaxProper on November 4, 2022, the company was servicing 115,000+ properties worth over $35 billion and processing more than $1 billion annually in property tax payments — all on $2.15 million in total capital raised.[1]
Opendoor acquired TaxProper for an 8-figure sum, making it a textbook example of capital-efficient execution in a niche vertical where regulatory complexity served as a durable moat.[2] The founding team subsequently departed Opendoor and launched FullSeam, accepted into YC's Winter 2026 batch — their second consecutive YC company.
Thomas Dowling arrived at Oxford in 2018 as a Rhodes Scholar, having graduated from the University of Illinois Urbana-Champaign with a degree in history and political science.[3] Before Oxford, he had served as a Municipal Finance Policy Advisor on Chicago Mayor Lori Lightfoot's transition team — a role that gave him direct exposure to how local governments set, contest, and collect property tax assessments.[4] That policy background was not incidental to TaxProper's founding; it was the origin of the insight.
His co-founder, Geoff Segal, brought a complementary technical skillset. Segal had worked as an actuarial statistician and research analyst at State Farm, where he built quantitative models of property risk and value — precisely the kind of statistical machinery needed to compare assessed values against market comparables at scale.[5] Dowling has described Segal as "another classmate from Illinois," suggesting the two knew each other before Oxford and reconnected around the idea.[6]
The founding insight was structural: property tax assessments are frequently inaccurate, the appeals process is well-established and legally accessible, but the friction of filing — understanding deadlines, gathering comparable sales data, completing county-specific paperwork — was high enough that most homeowners never bothered. Incumbent property tax attorneys existed but charged contingency fees that made them economically viable only for high-value commercial properties. The consumer market was essentially unserved by software.
Dowling and Segal applied to Y Combinator while Dowling was still at Oxford. The application succeeded. As Dowling later recalled: "I started working on a project that eventually grew into a software startup called TaxProper with another classmate from Illinois. We were accepted into a startup accelerator called YCombinator halfway through my first year at Oxford."[7]
TaxProper was incorporated in May 2019 and participated in YC's S19 batch, receiving the standard $150,000 in batch funding.[8] The company launched publicly at YC's S19 Demo Day in August 2019, pitching the B2C appeal automation product to investors. The founding team's domain pairing — municipal finance policy expertise plus actuarial statistical modeling — was unusually well-matched to a problem that required both regulatory navigation and quantitative accuracy.
Dowling was subsequently recognized on the Forbes 30 Under 30 list and appointed by Illinois Governor JB Pritzker to the Illinois Student Assistance Commission, reflecting the public profile he built during TaxProper's growth.[9]
May 2019 — TaxProper founded by Thomas Dowling and Geoff Segal in Chicago, IL.[10]
Summer 2019 — Accepted into Y Combinator S19 batch; receives $150K standard batch funding.[8]
August 2019 — TaxProper pitches at YC S19 Demo Day, presenting the B2C property tax appeal automation tool to investors.
June 5, 2020 — TaxProper raises $2M seed round led by Khosla Ventures, with Global Founders Capital, Clocktower Ventures, and angels participating. Product live in Cook County (Chicago) and 11 additional states. Average customer savings reported at ~$700 per appeal.[11]
2020–2022 — Company pivots from B2C homeowner tool to enterprise SaaS platform for institutional real estate operators; builds automated payment infrastructure, forecasting, and appeal management suite.
December 31, 2021 — TaxProper has 5 employees per Tracxn database snapshot.[12]
November 4, 2022 — TaxProper acquired by Opendoor Technologies (NASDAQ: OPEN) for an 8-figure sum. At acquisition, TaxProper services 115,000+ properties worth $35B+ and processes $1B+/year in property tax payments.[1]
November 2022 onward — Thomas Dowling continues as Director of TaxProper within Opendoor, managing multi-product tax data; company operates as a subsidiary.[13]
March 13, 2025 — Dowling gives interview to University of Illinois reflecting on TaxProper; confirms founding team has since launched FullSeam (YC W26).[14]
2025 — TaxProper founding team (Dowling, Segal, and founding engineer Aaron) co-found FullSeam, an AI agent platform for corporate accounting teams, accepted into YC W26.[15]
Phase 1: B2C Appeal Automation (2019–2020)
TaxProper's original product solved a specific, repeatable problem: most homeowners are overassessed on their property taxes and don't know it, and even those who do know it rarely file appeals because the process is opaque and time-consuming.
The product worked in three steps. A homeowner entered their property address. TaxProper's machine-learning algorithm then pulled comparable property assessments in the same jurisdiction and identified whether the subject property was assessed above market value relative to its neighbors.[16] If an overassessment was detected, TaxProper automatically generated the county-specific appeal paperwork and filed it on the homeowner's behalf — handling the bureaucratic friction that caused most eligible homeowners to do nothing.
Pricing was structured to minimize upfront risk for the customer: either a $149 flat fee (refundable if the appeal was unsuccessful) or a 30% contingency on first-year savings, mirroring the fee structure used by incumbent property tax attorneys but at a fraction of the cost.[17] The average savings per successful appeal was approximately $700.[18]
At the time of the June 2020 seed round, the product was live in Cook County and DuPage County in Illinois, plus counties in New York, California, Georgia, Florida, Hawaii, Missouri, Nevada, Pennsylvania, Tennessee, Utah, and Washington — 13 jurisdictions in total, each with its own filing rules and deadlines.[19] The geographic expansion itself was a technical challenge: property tax rules are set at the county level, meaning TaxProper had to encode the specific procedures, deadlines, and evidence requirements for each jurisdiction it entered.
Phase 2: Enterprise SaaS Platform (2020–2022)
The enterprise product was substantially broader than the appeal tool. It addressed the full property tax lifecycle for institutional operators managing large portfolios:
The technical core — the ML valuation engine capable of generating accurate property valuations for tax assessment purposes — carried over from the B2C product and was extended to handle institutional-scale data volumes.[22] By the time of acquisition, this infrastructure was processing over $1 billion annually in tax payments across 115,000+ properties.[23]
What differentiated TaxProper from generic property management software was the depth of its regulatory encoding. Property tax rules vary not just by state but by county, and in some cases by municipality within a county. Building a system that could accurately model, file, and pay across hundreds of jurisdictions simultaneously was a significant engineering and compliance undertaking — and one that created a meaningful barrier to replication.
TaxProper's B2C product targeted individual homeowners in jurisdictions with active appeal processes — primarily Cook County, Illinois, where Chicago's assessment practices had historically generated high rates of overassessment and a well-established appeals board. The expansion to 11 additional states by June 2020 suggests the team was testing geographic breadth before the pivot.
The enterprise product targeted institutional real estate operators: property managers, iBuyers, REITs, private equity real estate funds, and other entities managing portfolios of hundreds to thousands of properties. These customers shared a common characteristic — large, recurring property tax liabilities that were difficult to track, forecast, and pay accurately at scale. For an operator managing 10,000 properties across 50 counties, missing a tax payment deadline or failing to appeal an overassessment could mean tens of thousands of dollars in penalties or overpayments. The pain was real, recurring, and quantifiable.
Opendoor itself was the canonical customer: an iBuyer transacting thousands of homes simultaneously, with property tax exposure at every stage of the transaction cycle.
The U.S. property tax market is large and structurally fragmented. American homeowners and businesses pay approximately $600 billion in property taxes annually, administered by roughly 3,000 county-level taxing authorities.[24] The appeal market alone — the segment TaxProper initially targeted — is estimated at several billion dollars annually, historically dominated by local property tax attorneys and consulting firms operating on contingency.
The enterprise segment TaxProper ultimately served is harder to size precisely, but the $1B+ in annual payments TaxProper was processing at acquisition represents a meaningful slice of the institutional property tax payment flow. The total addressable market for property tax management software — including payment automation, forecasting, and appeal management for institutional operators — likely runs into the tens of billions of dollars in annual tax liability managed, with software fees representing a fraction of that.
TaxProper operated in a competitive landscape that looked different at each stage of its evolution.
In the B2C appeal market, the primary incumbents were local property tax attorneys and consulting firms operating on contingency — a fragmented, relationship-driven market with no dominant software player. The structural advantage TaxProper had was automation: it could process appeals at a cost structure that made the economics work for $700 average savings, where a human attorney could not. The risk was that this market was inherently local (county-by-county rules), seasonal (appeal windows are fixed), and had a low natural ceiling on per-customer revenue.
In the enterprise segment, TaxProper competed against a mix of legacy property tax consulting firms (Ryan LLC, Paradigm Tax Group), enterprise real estate software platforms (Yardi, MRI Software), and specialized proptech companies. The critical competitive axis was not feature completeness but regulatory depth: incumbents like Ryan had deep relationships with county assessors but lacked automated payment and forecasting infrastructure; enterprise real estate platforms had distribution but lacked property-tax-specific regulatory encoding.
TaxProper's position — deep regulatory knowledge encoded in software, combined with fintech-grade payment infrastructure — was difficult for either category of incumbent to replicate quickly. Legacy consultants would need to rebuild their delivery model around software; enterprise platforms would need to build the county-by-county regulatory layer from scratch. This structural moat, rather than any single product feature, appears to have been the primary driver of Opendoor's acquisition interest.
The competitive dynamic that made the enterprise pivot strategically sound was also the dynamic that made the B2C product structurally limited: the same regulatory complexity that created a moat for institutional software made consumer-scale distribution expensive and slow. Each new county required encoding new rules, new deadlines, and new filing formats — a cost that was easier to amortize across an enterprise client managing thousands of properties than across individual homeowners paying $149 each.
TaxProper operated two distinct revenue models across its two product phases.
B2C Phase: The company offered homeowners a choice between a $149 flat fee (refundable on loss) or a 30% contingency on first-year tax savings.[17] With average savings of ~$700 per appeal, the contingency model would generate approximately $210 per successful customer — a modest figure that required high volume to build meaningful revenue. The flat-fee model offered more predictable revenue but required the company to absorb appeal losses. TaxProper never disclosed B2C revenue figures, and the absence of any revenue metrics in the June 2020 seed announcement is itself a signal that the B2C unit economics were not the primary investment thesis.
Enterprise Phase: The enterprise pricing model was not publicly disclosed. Based on the product suite — payment automation, forecasting, assessment monitoring, and appeal management — the likely structure was a combination of per-property SaaS fees and/or a percentage of tax payments processed. At $1B+ in annual payments processed across 115,000+ properties, even a modest basis-point fee on payments would generate meaningful revenue. As an inference (not a confirmed figure): if TaxProper charged 10–20 basis points on payments processed, that would imply $1–2M in annual payment-processing revenue alone, before any SaaS subscription fees.
Capital efficiency: TaxProper raised $2.15M in total and achieved an 8-figure acquisition — a ratio that implies exceptional capital efficiency.[25] With 5–8 employees at the time of acquisition, annual burn was likely in the $1–2M range, suggesting the company may have been operating near breakeven or was revenue-funded by the time of the Opendoor deal. No ARR figures were publicly disclosed.
TaxProper's traction data is sparse for the B2C phase and more substantive for the enterprise phase.
B2C (2019–2020): The company reported average savings of ~$700 per appeal at the time of its seed round.[18] No customer count, appeal volume, or revenue figures were disclosed publicly. The geographic footprint at seed — 13 jurisdictions across 12 states — suggests the team was prioritizing coverage breadth over depth in any single market.
Enterprise (2020–2022): The metrics at acquisition tell a cleaner story:
These figures represent substantial operational scale for a company with 5–8 employees.[12] The ratio of properties managed to headcount implies a highly automated platform with minimal manual intervention per property — consistent with the product's design philosophy of encoding regulatory rules into software rather than relying on human consultants.
The headcount trajectory is notable: 5 employees as of December 2021, 8 listed on the YC company page, and an 8-figure acquisition in November 2022. TaxProper achieved institutional scale without institutional headcount — a direct consequence of the pivot from a service-intensive B2C model to a software-automated enterprise platform.
TaxProper did not fail. It is included here as a success case study — specifically, a case study in how a YC company identified the structural limits of its initial market, pivoted to a more defensible position, and executed a capital-efficient exit. The analysis below examines the decisions that drove that outcome.
The original B2C product was well-designed for its problem. But the economics of the consumer appeal market had a hard ceiling that no amount of execution could overcome.
The core constraint: average savings of ~$700 per appeal, with TaxProper capturing either $149 flat or $210 on a 30% contingency.[17] To build a $10M ARR business at $210 per customer, TaxProper would need approximately 47,600 paying customers annually. Property tax appeals are not a recurring monthly purchase — they happen once per assessment cycle, typically every one to three years depending on the jurisdiction. That means the effective addressable pool in any given year is constrained by both geography (which counties TaxProper had encoded) and the appeal calendar (fixed windows that vary by county).
Customer acquisition in this model is also inherently seasonal and local. A homeowner in Cook County has a specific window to file an appeal; outside that window, the product is irrelevant. This creates a marketing challenge — spend must be concentrated in narrow windows, in specific geographies, for a one-time purchase. The economics of paid acquisition against a $149–$210 revenue event are punishing.
The team appears to have recognized this ceiling by mid-2020. The $2M seed round, announced in June 2020, was the last external capital TaxProper raised — and the pivot to enterprise appears to have begun shortly thereafter.
The most consequential decision TaxProper made was identifying that its real competitive asset was not the consumer-facing appeal workflow but the underlying regulatory encoding engine — the system that mapped county-by-county property tax rules, deadlines, and filing requirements into software.
That asset was far more valuable to an institutional operator managing 10,000 properties across 50 counties than to a homeowner filing one appeal every three years. An institutional operator's property tax problem is not a one-time event; it is a continuous operational challenge involving payment scheduling, assessment monitoring, appeal identification, and forecasting for new acquisitions. The same regulatory complexity that made consumer-scale distribution expensive became a moat when amortized across enterprise contracts.
The pivot also unlocked a fundamentally different revenue model. Enterprise SaaS contracts are recurring, predictable, and scale with portfolio size — a much better fit for the underlying cost structure of a software platform that had already absorbed the fixed cost of encoding regulatory rules.
No specific trigger for the pivot has been publicly disclosed. The timing — between June 2020 and November 2022 — coincides with the iBuyer market's rapid expansion, which would have created a visible and growing cohort of institutional operators with exactly the property tax management problem TaxProper's platform could solve.
Opendoor's acquisition of TaxProper on November 4, 2022 was strategically coherent.[1] As an iBuyer transacting thousands of homes simultaneously, Opendoor had property tax exposure at every stage of its business: acquisition underwriting (forecasting future tax liability), holding period (paying taxes on inventory), and disposition (managing appeals on overassessed properties). TaxProper's platform addressed all three.
Thomas Dowling continued as Director of TaxProper within Opendoor after the acquisition, responsible for managing multi-product tax data — a structure consistent with an acqui-hire of both the team and the platform, not a pure technology acquisition.[27] As Dowling described it: "My cofounder and I grew TaxProper for several years before successfully exiting to Opendoor, a publicly traded company, in 2022. We ran the business as a subsidiary within Opendoor after the sale and continue doing so today."[13]
Opendoor's subsequent financial difficulties in 2023–2024 — the company's stock declined sharply as the iBuyer model faced rising interest rates and a cooling housing market — create uncertainty about what happened to TaxProper's product and team within the acquirer over the longer term. The founding team's eventual departure to launch FullSeam (YC W26) suggests they did not remain at Opendoor indefinitely, though the precise timeline of their departure is not publicly known.
TaxProper's decision to raise only $2.15M in total — and to execute a pivot, build enterprise infrastructure, and achieve an 8-figure exit on that capital — was not accidental. It reflects a deliberate operating philosophy.
With 5 employees as of December 2021 and 8 at acquisition, TaxProper's annual burn was likely in the range of $1–2M, implying the company had 12–24 months of runway from its June 2020 seed at any given time. This constraint forced the team to prioritize ruthlessly: build the regulatory encoding engine, automate the payment infrastructure, and sign enterprise contracts — rather than scaling a consumer marketing operation that would have burned cash without building a durable asset.
Dowling's public reflections on this period emphasize speed of execution over planning: "The most common startup failure mode is getting stuck in the planning phase; 90% fail before getting a single customer. The only way to learn if a particular idea will work is to launch the product and get it in front of your customer."[28] The B2C product, whatever its limitations, served as a forcing function — it got TaxProper in front of real customers, generated real data on the appeal market, and built the core valuation engine that the enterprise product later relied on.
One structural lesson from TaxProper's growth emerged clearly enough to motivate the founders' next company. As TaxProper scaled quickly, its internal accounting operations became a bottleneck: the team found itself "drowning in invoicing, reconciliations, customer questions, and exception handling."[29] This operational friction — a company that automated property tax payments for clients but struggled with its own back-office accounting — directly motivated FullSeam, an AI agent platform for corporate accounting teams.
The irony is instructive: TaxProper built sophisticated financial automation for its customers while its own internal finance operations remained manual. The gap between what TaxProper sold and what it used internally was large enough to become the founding insight for a second company.
Domain expertise encoded in software creates a moat that generalist platforms cannot easily replicate. TaxProper's founders brought municipal finance policy knowledge (Dowling) and actuarial statistical modeling (Segal) directly to the problem of property tax assessment. This allowed them to build a regulatory encoding engine — mapping county-by-county rules, deadlines, and filing requirements — that would have taken a generalist software team years to replicate. When Opendoor evaluated the build-vs-buy decision for property tax management, TaxProper's three years of regulatory encoding represented a genuine barrier.
The B2C product was a necessary step, not a failed strategy. TaxProper's consumer appeal tool generated the valuation engine, the regulatory data, and the operational knowledge that the enterprise platform was built on. Had the team tried to build enterprise property tax software from scratch without the B2C phase, they would have lacked the ground-level understanding of how county assessors actually process appeals. The B2C product was, in retrospect, a funded R&D phase for the enterprise pivot — a pattern that other vertical SaaS companies have used deliberately.
Raising less capital can force better capital allocation. TaxProper raised $2.15M in total and achieved an 8-figure exit — a ratio that most venture-backed companies never approach. The constraint of a small seed round prevented the team from scaling a consumer marketing operation that would have burned cash without building a durable asset. Instead, the capital went into the regulatory encoding engine and enterprise infrastructure that ultimately drove the acquisition. The lesson is not that all startups should raise less, but that in markets with high regulatory complexity and long enterprise sales cycles, capital efficiency can be a strategic choice rather than a limitation.
The operational problems you solve for customers will eventually become your own problems at scale. TaxProper automated property tax payments and reconciliations for institutional clients while its own internal accounting became a bottleneck as the company grew. The gap between the sophistication of TaxProper's customer-facing product and its internal operations was large enough to motivate a second company (FullSeam). Founders building financial automation products should audit their own back-office operations early — the pain they feel internally is often a signal about what their customers feel too.
Niche vertical exits can be highly capital-efficient even without venture-scale growth. TaxProper never raised a Series A, never disclosed revenue, and operated with fewer than 10 employees at acquisition. It achieved an 8-figure exit by building deep regulatory infrastructure in a niche that large incumbents had not prioritized and that generalist platforms could not easily replicate. The property tax management market is not a winner-take-all category — it rewards depth over breadth, and depth is achievable with a small, expert team.