ATS Assessor Treasurer Software

APIyesOSS—FREEyesDOCS4/5
AA7.2#1 of 17
—Web—Windows—Mac—Linux—Android—iOS

Ranked in Property Tax Software ·Free plan

About

ATS Assessor Treasurer Software is an open-source property tax application for calculating and collecting taxes. It manages assessments and levies for real and personal property, new construction and destroyed property, as well as bankruptcies, foreclosures and LIDs. Counties can set up payment and advance payment plans, configure accounting connections to existing software, and control whether late fees and NSF payments are assigned. The Personal Property Online module provides a public-facing site where business owners can update personal property information. Flexible queries and a general-purpose RESTful API support data access; the user interface also accesses data through that API. ATS works with Kitsap County’s MS SQL database without modifications. Other Entity Framework-supported databases can be used with a modification change. The software is presented as developed by Kitsap County, Washington, and the page says it remains in development, with the county considering making it available to other counties as open source. Velosys offers counties deployment assistance, customization, training and consultation; prices for those services are not shown.

Who it is for

ATS is aimed at counties managing property tax assessments and collections. Counties considering implementation can also seek deployment, customization, training and consultation from Velosys.

What is good

  • Manages real and personal property assessments
  • Supports payment and advance payment plans
  • Provides a public personal-property update module
  • Includes a general-purpose RESTful API
  • Freely available as open source

What to know first

  • The page says the software remains in development
  • Other supported databases require a modification change
  • Prices for implementation services are not shown

Inferse review

ATS Assessor Treasurer Software: the full review

ATS covers a broad set of county property tax workflows and exposes data through a RESTful API. Counties should account for its stated development status and confirm database fit and implementation service costs.

ATS Assessor Treasurer Software is a county property-tax system built around assessment, collection, and related office workflows. It is best suited to counties prepared to work with an open-source application and coordinate deployment or customization. Its broad tax-office scope costs nothing to license, but its development status makes it a less certain choice for teams seeking an established, broadly available product.

Overview

ATS addresses a wide range of county property-tax work, from assessments and levies to payment plans, accounting, and fee decisions. Its coverage of real and personal property, bankruptcies, foreclosures, and local improvement districts (LIDs) makes it more relevant to offices with varied cases than to teams seeking a narrow billing tool.

Kitsap County developed ATS, and the project remains in development there. Velosys offers deployment assistance, customization, training, and consultation for other counties. That support can help counties adapt the system, but prospective users should factor in the implementation work and confirm the project’s status and fit for their needs before committing.

Key features

  • Assessment and property records: ATS handles real and personal property, levies, new construction, destroyed property, bankruptcies, foreclosures, and LIDs. This range suits county offices with varied assessment and property situations.
  • Payment workflows: Payment plans and advance payment plans support staged collections. Counties can also control whether late fees and non-sufficient-funds (NSF) payments are assigned, leaving those decisions with local administrators.
  • Public personal-property updates: The Personal Property Online module gives business owners a public-facing website for updating personal property information. That provides a direct update channel for business records.
  • Accounting configuration: Counties can configure accounting and interface ATS with their existing accounting software. This is useful for offices that need tax workflows to connect with established accounting processes, though the precise integration fit will depend on the county’s setup.
  • Queries and API: Flexible queries support varied data retrieval, while a general-purpose RESTful API exposes ATS data. The user interface also accesses data through the API, an API-led design that may suit teams integrating the system with other software.
  • Database options: ATS works with Kitsap County’s MS SQL database without modifications. Other Entity Framework-supported databases can be used with a modification change, so counties using another database should confirm the required changes before planning deployment.

Pricing

The ATS plan costs 0.00 USD per free and is open source. This makes it a fit for counties prioritizing access to the software without a license charge. Customization, deployment, training, and consultation are available as services from Velosys; counties should account for those implementation needs separately when evaluating total cost.

Platforms

ATS is listed as an API platform. Its RESTful API is central to how the interface accesses data, which makes it relevant to teams considering integration, but the API designation alone does not establish compatibility with a county’s other systems.

Who it's for

ATS is aimed at county property-tax offices, particularly those managing both assessment and treasurer workflows and able to arrange implementation support. It is less compelling for counties that require a mature, broadly established deployment or cannot accommodate database modifications and local customization.

Pros and cons

  • Pros: Broad coverage across assessment, property events, and collections gives county offices a single system for varied tax workflows.
  • Pros: Open-source software at no license cost, paired with a RESTful API, offers counties room to work with the application and its data.
  • Pros: Configurable accounting, fee controls, and flexible queries can accommodate local administrative practices.
  • Cons: The software remains in development by Kitsap County, which makes its wider adoption a less certain fit for counties seeking an established product.
  • Cons: Counties using a database other than Kitsap’s MS SQL setup may need a modification change, adding a compatibility consideration to deployment.
  • Cons: Deployment and customization services may be needed, and their costs can affect the economics beyond the zero-cost software plan.

Alternatives

For other options, see Property Tax Software.

  • PVDNet Suite is a paid API and web option to consider when a county is comparing paid alternatives to ATS.
  • Cozerna RPTA is a paid option with API, Linux, self-hosted, and web platforms; choose it when those deployment environments are a priority.
  • DEVNET Edge combines CAMA, assessment administration, billing and collection, permitting and zoning, records management, wEdge, and EdgeMaps under all-inclusive pricing. It may suit teams seeking that broader package.
  • itamlink is a paid API and web alternative for teams considering another platform with demo-based pricing.
  • Avalara VAT Registration is a paid API and web alternative for readers comparing tax-related services.
  • CSC Corptax is enterprise corporate tax software, making it a different option for corporate tax needs.
  • Catalis Assessment E-file is a paid web alternative for readers considering another assessment e-filing product.
  • Springbrook Property Tax Management covers residential, commercial, agricultural, and personal property taxes from assessment through billing and collection, and is an alternative for teams seeking that scope across web and mobile platforms.

Verdict

ATS is a strong candidate for counties that need broad property-tax workflows, value open-source software, and can plan for implementation with Velosys. Its zero-cost plan and API-led design are meaningful advantages, but counties should look elsewhere if they need a mature, established deployment or cannot accommodate the project’s development status and database requirements.

Compared on property tax software

Free plan
Yesvelosys.com
Tax calculation
Yesvelosys.com
Assessment tools
Yesvelosys.com
API access
Yesvelosys.com

Facts

Purpose
ATS is an open-source, customizable property tax solution for calculating and collecting property taxes.velosys.com · 5 Oct 2026
Assessments and property
It manages assessments, levies, real and personal property, new construction and destroyed property, bankruptcies, foreclosures, and LIDs.velosys.com · 5 Oct 2026
Payment plans
It supports payment plans and advance payment plans.velosys.com · 5 Oct 2026
Public module
Its Personal Property Online module provides a public-facing website where business owners can update their personal property information.velosys.com · 5 Oct 2026
Accounting
The software lets counties configure accounting and interface with their existing accounting software.velosys.com · 5 Oct 2026
Fees and queries
Users can control whether to assign late fees and NSF payments, and can run flexible queries.velosys.com · 5 Oct 2026
API
ATS has a general-purpose RESTful API, and its UI accesses data through that API.velosys.com · 5 Oct 2026
Database
The page says ATS works with Kitsap County’s MS SQL database without modifications and that other Entity Framework-supported databases can be used with a modification change.velosys.com · 5 Oct 2026
Implementation support
Velosys offers counties deployment assistance, customization, training, and consultation.velosys.com · 5 Oct 2026
Intended users
The page presents ATS as a property tax management application developed by Kitsap County, Washington, and describes Velosys deployment assistance for other counties.velosys.com · 5 Oct 2026
Development status
The page says ATS is in development by Kitsap County and that Kitsap is considering making the project open source and available to other counties.velosys.com · 5 Oct 2026
Open source
The page describes ATS as open source and freely available.velosys.com · 5 Oct 2026
Fees and payments
Users can control whether late fees and NSF payments are assigned.velosys.com · 5 Oct 2026
Queries
ATS supports flexible queries.velosys.com · 5 Oct 2026
Implementation and support
Velosys offers counties assistance with deployment, customization, training, and consultation.velosys.com · 5 Oct 2026
Maker background
Velosys says it was founded in 2011 and is based in Poulsbo, Washington.velosys.com · 5 Oct 2026

Company

Maker headquarters
Velosys is based in Poulsbo, Washington.velosys.com · 5 Oct 2026
Founded
2011velosys.com · 28 Sept 2026
Headquarters
Poulsbo, Washington, United Statesvelosys.com · 28 Sept 2026

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