OpenSalesTax

OpenSalesTax is a self-hosted API for computing U.S. sales tax from public jurisdiction data. It is best for developers and small teams willing to run infrastructure and maintain tax inputs; businesses that need fully managed, audit-ready coverage should look elsewhere.

Overview

The service prices individual line items and can return tax apportioned across state, county, city, and district jurisdictions. Its documented categories cover general merchandise, clothing, groceries, prescription drugs, prepared food, and digital goods, giving implementers useful distinctions for common transaction types.

The project reports modules for 52 jurisdictions, with every published dump loading the 48 jurisdictions that levy sales tax. It builds those datasets from Streamlined Sales Tax files and state Department of Revenue publications rather than paid commercial feeds. That keeps the stack open and controllable, but users remain responsible for checking outcomes with the relevant state authority before remitting; the project expressly disclaims legal and tax advice.

Key features

Deployment and database choices

You can install the engine from source or run it with Docker. PostgreSQL is the default database, while MariaDB is supported as an optional extra. This is a practical fit for teams already operating those systems, but it is not a managed endpoint that removes database administration.

Authentication and traffic controls

Out of the box, access is open and limited per IP. An API-key mode instead requires an X-API-Key header and adds limits and usage tracking per key. Open access is convenient for internal prototypes; production integrations will generally want keyed access for attribution and more targeted throttling.

Data maintenance

Release dumps are tied to the Streamlined Sales Tax quarterly file current when each release is made. Documentation also describes fetching and loading newer source data, so operators can establish their own refresh process rather than waiting for a new application release.

Known calculation gaps

The project acknowledges incomplete sub-state stacking for Colorado home-rule cities and for Louisiana parish-level collectors. Those exceptions are material for merchants shipping into affected areas and rule out treating the API as a universal authority without validation.

Container caveat

The Docker runtime does not include the psql client. Restoring data therefore fails inside the container unless you add that package or use the source-install route, an operational wrinkle to resolve before standardizing deployments.

Pricing

Free / open source — free. The Apache 2.0, self-hostable plan provides the U.S. sales-tax calculation API at no charge. There are no paid tiers, seat allowances, trial windows, or renewal terms to weigh. The trade-off is operational: you supply hosting, database administration, data refreshes, and validation, and you absorb the impact of the documented jurisdiction gaps.

Platforms

OpenSalesTax is delivered as an API and can be self-hosted from source or with Docker. PostgreSQL is the standard persistence layer, with optional MariaDB support. It is therefore aimed at backend teams rather than buyers seeking a hosted web console.

Who it's for

Choose it for an engineering-led product that needs a no-license-cost U.S. sales-tax calculator, wants control over data and deployment, and can review rates against state guidance. It also suits contributors interested in reporting incorrect rates or adopting a state through the project's contribution process.

Look beyond it if your operation cannot maintain a database and refresh pipeline, needs complete local-tax stacking in Colorado and Louisiana, or wants a provider to assume compliance and filing responsibility. The public users registry currently shows no listed self-hosters or integrators, and the project is pre-1.0, so organizations requiring an established adoption record should factor that in.

Pros and cons

• Pro: No license fee and Apache 2.0 terms make the calculator inexpensive to embed and modify.
• Pro: State, county, city, and district breakdowns provide more actionable output than a single combined rate.
• Pro: API-key limits and usage tracking support controlled production access.
• Con: Colorado home-rule and Louisiana parish stacking is explicitly incomplete, which can affect destination-level accuracy.
• Con: Hosting, PostgreSQL operations, source-data loading, and tax verification remain your responsibility.
• Con: Docker restores need an added psql client or a source installation.

Alternatives

Vatstack is the better choice when you want an API with a web option and a free Developer plan offering unlimited quotes and dummy validations; its Launch plan starts at $0 per month with a stated allowance.

ShipVAT suits teams preferring a hosted API/web product, a free-forever tier, and a 100-call monthly allowance with a trial option.

VAT Engine is an alternative for buyers willing to use free access during an active alpha, with availability, limits, support, pricing, and features subject to change.

Zamp fits teams seeking a 30-day sandbox and a paid U.S. compliance offering aimed at scaling organizations.

Kintsugi is aimed at global nexus monitoring, exposure auditing, and risk assessment rather than only a self-hosted calculation engine.

CCH SureTax is for organizations wanting technology with optional filing and remittance, including a fully outsourced tier.

CCH Tagetik is a paid self-hosted and web platform sold through demo or quote discussions.

Complyt is a paid API and web alternative.

Browse more options in Tax Engine Software.

Verdict

OpenSalesTax is a strong starting point for technically capable teams that value open-source control and zero licensing cost for U.S. sales-tax calculations. Choose it for jurisdiction-level API output and ownership of the deployment; choose another provider when incomplete local stacking, pre-1.0 maturity, or the burden of maintaining tax data creates unacceptable compliance risk.