# Best sales tax and VAT calculation APIs for AI agents > Avalara AvaTax (B), Anrok (C) and Kintsugi (C) lead the 10 ranked sales tax and VAT calculation APIs. Picks by need, strengths, weaknesses and prices from the Anchor benchmark. - Canonical: https://www.anchorterminal.com/best/tax/ - Markdown: https://www.anchorterminal.com/best/tax/index.md (~6,350 tokens) - Slim: https://www.anchorterminal.com/best/tax/index.min.md (~1,430 tokens, same facts, less prose, for token-sensitive contexts) - JSON: https://www.anchorterminal.com/best/tax/index.json (this page as data, same URL with Accept: application/json) - Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt) - API: https://www.anchorterminal.com/api/v1/index.json - Updated: 2026-10-08 All 10 ranked sales tax and VAT calculation APIs on the Anchor benchmark, with a pick for each need and where each one falls short. Scores come from public evidence, re-checked as vendors change. - Ranked: 10 · agent-ready (BB or better): 0 · accept x402: 0 · hosted endpoints: 10 - Full ranked table: https://www.anchorterminal.com/categories/tax.md - Head-to-head comparisons: https://www.anchorterminal.com/compare/tax/index.md (45) - Methodology: https://www.anchorterminal.com/benchmark/index.md ## The shortlist | # | Tool | Grade | Score | Best for | Price | Where | | --- | --- | --- | --- | --- | --- | --- | | 1 | [Avalara AvaTax](https://www.anchorterminal.com/tools/avalara.md) | B | 68.8 | An agent that must calculate and record US sales tax at address level, with VAT and GST in other countries, and hand the records to filing. | $79 / mo | hosted | | 2 | [Anrok](https://www.anchorterminal.com/tools/anrok.md) | C | 61.6 | An agent working for a software or ecommerce seller that already uses Anrok and wants calculation, exemption certificates and filing status in one account. | $100 / mo | hosted | | 3 | [Kintsugi](https://www.anchorterminal.com/tools/kintsugi.md) | C | 60.7 | An agent working for a seller that already has Kintsugi Premium and wants estimates, transaction sync, exemptions, nexus, registrations and filing status through one API, or read-only answers about an account through the OAuth MCP server. | $75 / tx | hosted | | 4 | [Quaderno](https://www.anchorterminal.com/tools/quaderno.md) | C | 59.5 | An agent working for a SaaS, digital-goods or e-commerce seller that needs a tax rate at checkout, a record of each sale with location evidence, and compliant invoices, including Spanish Verifactu and TicketBAI. | $29 / mo | hosted | | 5 | [TaxJar](https://www.anchorterminal.com/tools/taxjar.md) | C | 57.6 | An agent working for a US seller that needs sales tax on an order at checkout and a record of orders and refunds for state reporting, with exempt customers handled by ID. | $99 / mo | hosted | | 6 | [TaxCloud](https://www.anchorterminal.com/tools/taxcloud.md) | C | 57.4 | An agent working for a US seller that needs tax on a cart at checkout, a record of orders and refunds for filing, and exemption certificates by customer. | $79 / mo | hosted | | 7 | [Vertex O Series](https://www.anchorterminal.com/tools/vertex-tax.md) | C | 54.7 | An agent working inside a company that already has an O Series licence, for quotes, invoice tax, tax area lookups and tax configuration across sales tax, use tax and VAT. | Paid | hosted | | 8 | [Fonoa](https://www.anchorterminal.com/tools/fonoa.md) | D | 51.7 | An agent working for a company that already has a Fonoa contract and needs tax ID validation, VAT or GST calculation, or e-invoice reporting across many countries through one API. | Paid | hosted | | 9 | [Zamp](https://www.anchorterminal.com/tools/zamp.md) | D | 49.5 | An agent working for a US or Canadian seller that wants Zamp's team to register, file and remit, and needs calculation and transaction sync through a small API. | Paid | hosted | | 10 | [Numeral](https://www.anchorterminal.com/tools/numeral.md) | D | 49.3 | An agent working for a seller or platform that has a Numeral account and needs tax at checkout, committed transactions for filing, and read access to nexus, registrations and filings through MCP. | $75 / tx | hosted | ## Picks by need - Highest score overall: [Avalara AvaTax](https://www.anchorterminal.com/tools/avalara.md), B, 68.8/100 on the benchmark. Also [Anrok](https://www.anchorterminal.com/tools/anrok.md), C, 61.6/100. - Reliability: [Quaderno](https://www.anchorterminal.com/tools/quaderno.md), 91/100 on reliability, against 62 for the overall leader. - Schema & documentation: [Kintsugi](https://www.anchorterminal.com/tools/kintsugi.md), 87/100 on schema & documentation, against 85 for the overall leader. ## How to choose - Jurisdiction coverage by tax type: Check which countries and US states each tool covers for sales tax, VAT and GST, since a jurisdiction left out is a gap the agent has to handle itself. - Exemption certificates and reuse: Check how exempt buyers and their certificates are stored and applied to later calculations, since an agent that sells to exempt customers needs the exemption to carry forward. - Address mapping and rate checks: Check how a transaction's address is validated and mapped to a jurisdiction, and whether the rate returned can be compared with the published rate, before any tax is committed. - Commit step and filing report: Check whether a calculated transaction can be committed for reporting and what the resulting report contains, since a quote that is never committed leaves nothing to report. - How the benchmark tests this category: The same twenty transactions (US states, EU countries, digital and physical goods, an exempt buyer) sent to each listing's calculation API and committed for reporting. We check the rates returned against published rates, address handling and the report that results. In this run listings are graded from public evidence against the published checklist. ## Each one in detail ### 1. Avalara AvaTax, B 68.8/100 Avalara AvaTax calculates sales tax, VAT and GST for a transaction and records it for reporting. Agents reach it through the AvaTax REST v2 API or a hosted MCP server, with separate Avalara products for returns, exemption certificates and e-invoicing. - Verdict: The REST API has a public Swagger file with 491 operations, a Markdown page per endpoint and a 90-day trial with no card. Production rate limits and prices per transaction are not published, the API patch notes stop at April 2023, and the tax calculation service was degraded for about 23 hours on 5 and 6 October 2026. - Choose it for: An agent that must calculate and record US sales tax at address level, with VAT and GST in other countries, and hand the records to filing. - Strength: Public Swagger 2.0 file with 491 operations, plus llms.txt and a Markdown page with a curl example for each endpoint - Strength: Hosted MCP server at mcp.avalara.com/avatax with ten documented tools, OAuth sign-in and an entry in the official MCP registry as com.avalara/avatax - Strength: 90-day AvaTax trial with no card, limited to 5 orders and 5 invoices a minute and 1,000 transactions a day - Weakness: Production rate limits are not published. The only numbers found are the trial limits and 5 calls a minute on report exports - Weakness: No price per transaction. Public plans are $79 a state a month, or $69 with SST services, and larger accounts are quoted - Weakness: The API patch notes page ends at version 23.4.1 of 26 April 2023, while production reports 26.9.2 - Price: $79 / mo · Auth: OAuth or key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/avalara.md ### 2. Anrok, C 61.6/100 Anrok is a hosted sales tax, VAT and GST compliance platform for software and ecommerce sellers. Its API calculates tax and records transactions, and Anrok registers, files and remits. A remote MCP server gives AI assistants access to the account. - Verdict: The public OpenAPI 3.1 spec covers 26 operations with typed error codes, and the remote MCP server uses OAuth 2.1 with six scopes and keeps voids, refunds and filing approval away from the model. Access needs a seller account arranged through sales, API keys carry no scopes, and no API changelog, SDK or subprocessor list was found. - Choose it for: An agent working for a software or ecommerce seller that already uses Anrok and wants calculation, exemption certificates and filing status in one account. - Strength: Public OpenAPI 3.1 spec at apidocs.anrok.com/openapi.yaml with 26 operations, 45 enums and typed error codes on 409 responses - Strength: Remote MCP server at mcp.anrok.com/mcp with OAuth 2.1, PKCE, dynamic client registration, six scopes and a revocation endpoint - Strength: MCP has no void, negation or filing-approval tool, and Anrok says all write operations are audited - Weakness: No self-serve signup. Starter is $100 per market a month through "Talk to us", and Custom is quoted by sales - Weakness: API keys have a note and an enabled switch only. No scopes, read-only mode or expiry found in the help centre article - Weakness: No API changelog, deprecation policy or official SDK found. The spec is version 1.1 with no dated history - Price: $100 / mo · Auth: OAuth or key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/anrok.md - Against #1: https://www.anchorterminal.com/compare/anrok-vs-avalara.md ### 3. Kintsugi, C 60.7/100 Kintsugi is a hosted sales tax, VAT and GST compliance platform. Its API estimates tax, records transactions, customers and exemptions, and manages nexus, registrations and filings. Two MCP servers connect AI assistants to the API and to account data. - Verdict: The docs are built for machine readers, with llms.txt, Markdown pages, a public OpenAPI 3.1 file, a dated changelog and an MCP server whose 55 tools carry read-only and destructive annotations. API keys need the custom-priced Premium plan and carry no scopes, no general rate limit is published, and breaking changes reached the pinned 2026-07-21 release in October 2026. - Choose it for: An agent working for a seller that already has Kintsugi Premium and wants estimates, transaction sync, exemptions, nexus, registrations and filing status through one API, or read-only answers about an account through the OAuth MCP server. - Strength: Docs served for agents. `llms.txt` indexes 682 pages, every page has a `.md` twin, and `llms-full.txt` holds the full text - Strength: Public OpenAPI 3.1 file at `https://api.trykintsugi.com/openapi.json`, readable without a key, with 901 operations and 1,325 schemas - Strength: The MCP server at `https://docs.trykintsugi.com/mcp` lists 55 tools, each with readOnlyHint, destructiveHint and idempotentHint set - Weakness: API access, SDKs and real-time tax calculation are listed only under Premium, which is priced on request. API keys need a paid plan that includes them - Weakness: Nine changelog entries from 17 September to 7 October 2026 are marked breaking, five on the pinned 2026-07-21 release and four on v1. No advance notice was found - Weakness: No general rate limit is published and no `Retry-After` header is documented. The docs say only to retry 429, 500 and 503 with backoff - Price: $75 / tx · Auth: OAuth or key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/kintsugi.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-kintsugi.md ### 4. Quaderno, C 59.5/100 Sales tax, VAT and GST software for online businesses from Recrea Systems, a Visma company in Spain. Its REST API calculates tax for a sale, records sales and refunds, issues invoices and credit notes and exports tax reports. - Verdict: A public OpenAPI 3.1 spec covers 92 operations, with a free sandbox and a status page showing no incident since July 2025. The API key has full account access, there are no idempotency keys, and the newest public API version is dated October 2024. - Choose it for: An agent working for a SaaS, digital-goods or e-commerce seller that needs a tax rate at checkout, a record of each sale with location evidence, and compliant invoices, including Spanish Verifactu and TicketBAI. - Strength: Public OpenAPI 3.1 spec with 92 operations across tax rates, transactions, invoices, credit notes, reporting and webhooks - Strength: Separate free sandbox at sandbox-quadernoapp.com with test tax IDs and a purge endpoint, and a 7-day production trial without a card - Strength: Statuspage with API and web application components and no incident recorded since 16 July 2025 - Weakness: One API key reads and writes everything its user can reach. Scopes exist only on Connect OAuth tokens (read_only, read_write) - Weakness: No idempotency keys, and the docs say retry logic is the integration's responsibility - Weakness: The newest public API version is 20241028. A preview of 20260309 is in the docs but not yet available - Price: $29 / mo · Auth: OAuth or key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/quaderno.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-quaderno.md ### 5. TaxJar, C 57.6/100 TaxJar is Stripe's US sales tax service for businesses that sell across states. Its REST API calculates tax for an order, looks up rates by address, records orders and refunds for reporting, and stores exempt customers. - Verdict: A 21-operation REST API with a no-card 30-day trial, caller-chosen transaction IDs that make order pushes safe to repeat, and no status-page incident since March 2026. No OpenAPI spec or llms.txt was found, the API changelog stops at January 2022, tokens carry no scopes, and calculation is US-only for new accounts. - Choose it for: An agent working for a US seller that needs sales tax on an order at checkout and a record of orders and refunds for state reporting, with exempt customers handled by ID. - Strength: 30-day trial with Professional plan access, the API included, and no card needed at signup - Strength: Orders and refunds take a caller-chosen `transaction_id`. A duplicate create returns 422 and the docs direct a PUT update - Strength: status.taxjar.com lists seven components and no incident since 26 March 2026 - Weakness: No OpenAPI spec or llms.txt was found. The taxjar/openapi repository on GitHub holds only a README - Weakness: The API changelog's last entry is 24 January 2022, and no deprecation policy was found - Weakness: Calculation covers the United States only for new accounts. The docs point other countries to Stripe Tax - Price: $99 / mo · Auth: API key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/taxjar.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-taxjar.md ### 6. TaxCloud, C 57.4/100 TaxCloud is a US sales tax service from The Federal Tax Authority, LLC. Its v3 REST API calculates tax on carts, records orders and refunds for filing, stores exemption certificates, verifies addresses and searches product tax codes. - Verdict: A 30-operation REST API with a public OpenAPI 3.1 contract, llms.txt, Markdown docs and a 30-day trial that needs no card. The vendor publishes no rate limit numbers, no SLA, no API changelog and no official v3 client library, and the security page names no audit or certification. - Choose it for: An agent working for a US seller that needs tax on a cart at checkout, a record of orders and refunds for filing, and exemption certificates by customer. - Strength: OpenAPI 3.1 documents for the Sales Tax API (16 operations) and Management API (14), plus llms.txt and a Markdown copy of every docs page - Strength: 30-day trial with Premium plan access, the API included, and no card or payment method needed - Strength: Refunds take an `idempotencyKey`, carts upsert by `cartId`, and a repeated void returns 204 - Weakness: No rate limit numbers are published. The API page says only that the threshold is high and subject to change - Weakness: The security page says TaxCloud does not offer an SLA, and the terms supply the service as is - Weakness: No API changelog or deprecation policy was found, and the legacy v1 API has no published end date - Price: $79 / mo · Auth: API key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/taxcloud.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-taxcloud.md ### 7. Vertex O Series, C 54.7/100 Vertex O Series is indirect tax software from Vertex, Inc. that calculates sales tax, use tax and VAT for a transaction and records it for reporting. Agents reach it through REST v2 APIs with OAuth client credentials. - Verdict: Public OpenAPI 3.0 specs cover calculation, transaction management, tax area lookup and tax configuration, and guides are served as Markdown. Access needs a sales contract. No price, free tier, sandbox signup, calculation rate limit, idempotency key or official SDK was found in the reviewed documentation. - Choose it for: An agent working inside a company that already has an O Series licence, for quotes, invoice tax, tax area lookups and tax configuration across sales tax, use tax and VAT. - Strength: OpenAPI 3.0 specs download without a login. Calculation and Tax GIS is version 2.9.0 with 14 operations, Tax Configuration v2.1.0 with 29 - Strength: Every guide page is served as Markdown when .md is added to its URL - Strength: Each Cloud API credential maps to one API and one partition, and token requests carrying credentials in the URL are rejected - Weakness: No public price, free tier or self-serve signup. The security guide sends new users to the Vertex sales team for an account - Weakness: No rate limit for the calculation API and no idempotency key were found in the reviewed documentation - Weakness: The standard token endpoint allows 10 access token requests per 8 hours for each client - Price: Paid · Auth: OAuth · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/vertex-tax.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-vertex-tax.md ### 8. Fonoa, D 51.7/100 Fonoa is a hosted indirect tax platform for VAT, GST and sales tax. Its REST API validates tax identification numbers, calculates tax on a transaction and reports e-invoices to tax authorities, with a sandbox and a demo environment. - Verdict: The API reference is served as Markdown with an OpenAPI definition on each endpoint page, and e-invoicing submissions are idempotent by `transaction_id`. API keys are issued by Fonoa staff after contact, no price, rate limit or changelog is published, and the only public terms date from May 2020 and cover older seller sites. - Choose it for: An agent working for a company that already has a Fonoa contract and needs tax ID validation, VAT or GST calculation, or e-invoice reporting across many countries through one API. - Strength: Every reference page is served as Markdown with its OpenAPI 3.0 definition inline, indexed by docs.fonoa.com/llms.txt - Strength: E-invoicing submissions are idempotent by `transaction_id`, and the docs say a transaction can be replayed any number of times - Strength: The sandbox at sandbox.fonoa.com returns fixed outcomes for documented test inputs, including errors, delays and HTTP 500 - Weakness: No self-serve signup. Sandbox, demo and production keys are issued by Fonoa after contact by email or the sales form - Weakness: No pricing page. www.fonoa.com/pricing returns 404 and the site's buttons read "Get in touch" - Weakness: No rate limit numbers found. The 429 response says "Try again a bit later" with no `Retry-After` documented - Price: Paid · Auth: API key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/fonoa.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-fonoa.md ### 9. Zamp, D 49.5/100 Zamp is a managed sales tax service for US and Canadian sellers. Its REST API calculates tax by address, records transactions for filing and reads registrations and filings, while Zamp's team registers, files and remits. - Verdict: A free 30-day sandbox key needs no card or sales call, and the docs are served as Markdown with llms.txt and a published limit of 1,000 requests a minute. There is no OpenAPI file, SDK, API changelog or published price, production keys come with a sales-led account, and the site footer says SOC 2 compliance is in progress. - Choose it for: An agent working for a US or Canadian seller that wants Zamp's team to register, file and remit, and needs calculation and transaction sync through a small API. - Strength: Free 30-day sandbox key by email with no card or sales call, preloaded with all 47 remote-seller state registrations - Strength: Docs served as Markdown with `llms.txt` and `llms-full.txt`, and cURL, Node.js and Python examples in the quickstart - Strength: Published limit of 1,000 requests a minute, and responses carry `x-zamp-rate-limit-remaining` and `x-zamp-rate-limit-reset` headers - Weakness: No OpenAPI file for the API. The one file on the docs host is the documentation platform's plant store sample - Weakness: No price is published. The U.S. and U.S. + Canada plans read "Contact sales", and production keys come with a Zamp account - Weakness: No API changelog, version in the path, deprecation policy or official SDK found in the reviewed documentation - Price: Paid · Auth: API key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/zamp.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-zamp.md ### 10. Numeral, D 49.3/100 Numeral is a hosted sales tax and VAT compliance service from Numeral Two, Inc. Its REST API calculates tax, records transactions and refunds, and manages exempt customers, and Numeral registers and files. A remote MCP server reads the account. - Verdict: Docs are written for agents, with a public OpenAPI spec for 32 operations, Markdown pages, llms.txt and a remote MCP server whose 14 tools are read-only by default. No status page, numeric rate limit or SLA was found, the API ignores idempotency keys, and API access is sold on a custom plan after a demo. - Choose it for: An agent working for a seller or platform that has a Numeral account and needs tax at checkout, committed transactions for filing, and read access to nexus, registrations and filings through MCP. - Strength: Public OpenAPI 3.0.1 spec for version 2026-03-01 with 32 operations, 74 schemas and 57 enums, plus llms.txt and a Markdown copy of every docs page - Strength: Remote MCP server at `https://mcp.numeralhq.com/mcp` documents 14 read-only tools. Four write tools are off by default and absent from `tools/list` until enabled - Strength: Date-versioned API selected with the `X-API-Version` header, with a changelog and migration notes for each of four versions - Weakness: No status page, uptime SLA or numeric rate limit was found. The product page says rate limits can be removed on request - Weakness: The API ignores an `Idempotency-Key` header. A retried commit is safe only if the client handles `REFERENCE_ORDER_ID_ALREADY_EXISTS` - Weakness: Secret keys carry no scopes, and the MCP server has no OAuth flow. One key reads all of the account's tax data - Price: $75 / tx · Auth: API key · x402: no · Where: hosted - Full assessment: https://www.anchorterminal.com/tools/numeral.md - Against #1: https://www.anchorterminal.com/compare/avalara-vs-numeral.md ## Head to head - [Anrok vs Avalara AvaTax](https://www.anchorterminal.com/compare/anrok-vs-avalara.md) - [Avalara AvaTax vs Kintsugi](https://www.anchorterminal.com/compare/avalara-vs-kintsugi.md) - [Avalara AvaTax vs Quaderno](https://www.anchorterminal.com/compare/avalara-vs-quaderno.md) - [Avalara AvaTax vs TaxJar](https://www.anchorterminal.com/compare/avalara-vs-taxjar.md) - [Anrok vs Kintsugi](https://www.anchorterminal.com/compare/anrok-vs-kintsugi.md) - [Anrok vs Quaderno](https://www.anchorterminal.com/compare/anrok-vs-quaderno.md) - [Anrok vs TaxJar](https://www.anchorterminal.com/compare/anrok-vs-taxjar.md) - [Kintsugi vs Quaderno](https://www.anchorterminal.com/compare/kintsugi-vs-quaderno.md) - [Kintsugi vs TaxJar](https://www.anchorterminal.com/compare/kintsugi-vs-taxjar.md) - [Quaderno vs TaxJar](https://www.anchorterminal.com/compare/quaderno-vs-taxjar.md) ## Questions ### What are the highest-rated sales tax and VAT calculation APIs for AI agents? Avalara AvaTax has the highest benchmark score of the 10 ranked sales tax and VAT calculation APIs, 68.8 (B). Anrok is second with 61.6 (C). ### How many sales tax and VAT calculation APIs are agent-ready? 0 of the 10 ranked here grade BB or better, the bar for agent-ready on the Anchor benchmark. ### Which sales tax and VAT calculation APIs accept x402 payments? None of the ranked listings here accepts x402 for its main call yet. ### How is this list ranked? By the Anchor benchmark score out of 100, a weighted mean of the scored categories minus deductions for negative events, from public evidence re-checked as vendors change. Listings cannot pay for a place. The latest assessment behind this page is from 8 October 2026. ## How this list is made The order is the Anchor benchmark score, the same number as on each listing. Each listing is graded from public evidence against the benchmark checklist, and the picks are worked out from those grades, prices and facts. No listing pays for its place, and paid audits or listing help never change a score.