API changelog
Every change to the Kintsugi API and every release, newest first. Breaking changes carry the Breaking change mark. Tenanted releases are dated, and you choose one with the Api-Version header.
Changes
2026-10-07
Breaking changesLimits billing changes to an organization's Owners, Admins and own API keyBillingBreaking change
POST /billing/checkout, POST /billing/portal-session, PATCH /billing/plan and PATCH /billing now accept only the organization's own Owners and Admins and the organization's own API key. Any other caller that can reach the organization, including a Member, a partner user and a portfolio or reseller key, answers 403 with code forbidden; these callers were accepted before. A user acting through a portfolio is refused the same way. An organization you cannot access still answers 404, and the billing read endpoints are unchanged.
- Start checkouts, portal sessions and plan changes from the organization's own Owner or Admin session, or with its organization API key.
- Handle
403with codeforbiddenfrom these four endpoints.
Releases
2026-10-06
LatestTenanted APIConsistent country codes, empty values and status casing
2026-10-06 makes the Tenanted API more predictable to build on. Every country code is now countryCode, a value that is not set is null rather than an empty string, and status and type values are uppercase throughout. Integrations pinned to 2026-07-21 are unaffected until you choose to move, and the table below lists everything that changes when you do.
Compared with 2026-07-21
| Change | Applies to | 2026-07-21 | 2026-10-06 |
|---|---|---|---|
| Country code field | Addresses, customers, transactions, tax estimates and billing usage, in requests and responses | country | countryCode. Query parameters named country keep their name. |
| State on nexus exposure events | GET /nexus/{nexus_id}/exposure-history | state | stateCode, always present |
| State of a country-level filing | stateCode and stateName on every filing | Empty string | null |
| Organization state and country when not set | state and countryCode on organizations, and state in organization lists | Empty string, always present | null, and may be omitted |
| Exemption with no match on a certificate upload | exemptionId on missing-certificate upload results | Empty string | null |
| Missing-certificate status values | Upload, upload status and public confirm-upload results | Lowercase: processing, satisfied, rejected | Uppercase: PROCESSING, SATISFIED, REJECTED, plus PENDING on the public landing page |
| Exemption type when approving certificate imports | POST /certificate-imports/{certificate_import_id}/approve and POST /certificate-imports/bulk-approve | Any text, defaulting to customer | CUSTOMER, WHOLESALE, TRANSACTION or REVERSE_CHARGE, defaulting to CUSTOMER. Any other value returns 422. |
| Security questions in a credential reveal | fields on POST /registrations/{registration_id}/credentials/reveal | security_questions | securityQuestions |
| Line item with no product name | productName on transaction lines | null | Empty string |
| Help article label on back-filing options | GET /filings/backFilingRequest/options | Text or null | Always text |
| Job ID on bulk filing results | POST /filings/bulk/approve and POST /filings/bulk/pause | jobId, always null | Removed |
Moving an integration from 2026-07-21
- Send
Api-Version: 2026-10-06with each request you move. Requests without it keep running against 2026-07-21. - Rename
countrytocountryCodewherever you send or read an address, customer, transaction or tax estimate. - Treat
nullas "not set" for filing and organization locations and for an unmatchedexemptionId, and an emptyproductNameas "no product name". - Compare missing-certificate statuses in uppercase, and send
exemptionTypein uppercase when you approve certificate imports. - Read
stateCodeon nexus exposure events, requestsecurityQuestionswhen you reveal registration credentials, and stop readingjobIdon bulk filing results.
2026-07-21
Tenanted APIIntroducing the Tenanted API
A fresh foundation for building on Kintsugi. The Tenanted API is versioned by date, and you choose the release you build against. It speaks one consistent dialect from end to end: clean paths, camelCase fields, exact decimal amounts, and a single error format. And it is built for scale, with one credential reaching every organization it owns.
Compared with v1
| Topic | v1 | 2026-07-21 |
|---|---|---|
| Versioning | The /v1 path prefix | The Api-Version header, dated YYYY-MM-DD. Optional; without it, a request runs against the launch release |
| Paths | /v1/transactions | /transactions |
| Authentication | x-api-key | Api-Key. Endpoints that manage people accept a signed-in session token instead |
| Choosing an organization | x-organization-id, required on almost every request | One credential reaches every organization it owns. Narrow a request with Organization-Id, Connection-Id, or Entity-Id |
| Field names | snake_case | camelCase |
| Money and rates | Decimal strings out, numbers or strings in | Decimal strings at a fixed scale: amounts to 2 places, rates to 9 |
| Timestamps | No single documented format | RFC 3339 in UTC, always ending in Z |
| Errors | Shapes vary by endpoint | One envelope everywhere: code, message, requestId, and errors |
| Portfolio | Not available | Portfolio and Portfolio Reseller endpoints, for partner accounts |
Moving an integration from v1
- Send
Api-Versionwith every request, pinned to the release you build against (the newest is2026-10-06), so your integration stays on it until you decide to move. - Drop
/v1from your paths. - Send your key as
Api-Key, and replacex-organization-idwithOrganization-Idwherever you target one organization. - Rename fields to camelCase, and read every amount as a decimal string, never a float.
- Branch on the error
code, not the message or the HTTP status, and quoterequestIdwhen you contact support.
Creating a transaction answers 202 Accepted straight away, and tax is calculated just after. Check processingStatus before you read the tax totals.
v1
LegacyThe original Kintsugi API, versioned in the path. It is documented exactly as before, so existing integrations can keep running with confidence. New integrations should start on the newest Tenanted API release.