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Centsless is a REST API. Every request goes to the base URL below, and every endpoint except GET /health and GET /version requires an x-api-key header. Requests and responses use JSON throughout, with the single exception of POST /export, which returns a CSV file.

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Base URL

https://api.centsless.org/api/v1

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Authentication

Pass your API key in the x-api-key request header on every call that requires authentication. 
curl https://api.centsless.org/api/v1/transaction \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "merchant_id": "MERCHANT-001", ... }'
Keys are role-scoped. Merchant keys authorize transaction processing, auditor keys grant read-only access to compliance data, and admin keys provide full platform access. See the Authentication page for the full key type reference.
API keys are shown once at creation and hashed with SHA-256 before storage. Store them in a secrets manager immediately — they cannot be retrieved later.

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API version

The current API version is 3.6.0. The version is also available at runtime from GET /version, which returns the engine version and available endpoints without requiring authentication.

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Rate limits

Rate limits are enforced per API key.
EnvironmentLimit
Sandbox1,000 requests / hour
Production10,000 requests / hour
When you exceed the limit, the API returns 429 Too Many Requests. See Error codes for the full error schema.

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Request format

Set Content-Type: application/json on all requests that include a body. The API rejects requests with a malformed or missing content type. 
Content-Type: application/json

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Endpoints that do not require authentication

The following endpoints are open and do not require an x-api-key header:
MethodEndpointDescription
GET/healthPlatform status, database connectivity, and compliance certifications
GET/versionCurrent API version, engine version, and available endpoints

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Explore the API

Transactions

Process cash transactions with jurisdiction-aware rounding, query transaction history, and manage voids and refunds.

Jurisdiction

Resolve rounding rules by ZIP code, state, county, or city using the 33,000+ ZIP code Census database.

Tipping

Record and pool tips with FLSA-compliant rounding, process payouts, and detect wage theft patterns.

Compliance & Audit

Query immutable audit logs, verify hash chain integrity, and run void and override analytics.