> ## Documentation Index > Fetch the complete documentation index at: https://docs.3ringscapital.co/llms.txt > Use this file to discover all available pages before exploring further. # Post a journal entry > Post a double-entry journal. The sum of debits must equal the sum of credits; we validate and balance server-side before anything touches the ledger. Always send an `Idempotency-Key` so a retried request never double-posts. ## OpenAPI ````yaml /openapi.json post /v1/journals openapi: 3.1.0 info: title: 3Rings API version: 1.0.0 summary: Embedded double-entry accounting infrastructure. description: >- The 3Rings API lets you embed real double-entry accounting into your product. Create a business you serve, provision its chart of accounts, post balanced journals, and read financial statements — all on the same guarded core that powers 3Rings. All amounts are **integers in the currency's minor unit** (e.g. kobo for NGN, cents for USD). All write endpoints accept an `Idempotency-Key` so retries are safe. Balancing and posting are authoritative on our side: you send the intent, we keep the books correct. contact: name: 3Rings Developer Support url: https://docs.3ringscapital.co/support email: developers@3ringscapital.co license: name: Proprietary url: https://3ringscapital.co/terms-of-use servers: - url: https://api.3ringscapital.co description: Production - url: https://api-sandbox.3ringscapital.co description: Sandbox security: - bearerAuth: [] tags: - name: Businesses description: >- The businesses you serve, modelled as sub-accounts under your partner account. - name: Chart of Accounts description: The ledger accounts each business posts against. - name: Journals description: >- Double-entry journal entries. Debits and credits must balance; we enforce it server-side. - name: Statements description: Trial balance, profit & loss and balance sheet, computed from the ledger. - name: Categorization description: Classify a transaction into a chart-of-accounts category with AI. paths: /v1/journals: post: tags: - Journals summary: Post a journal entry description: >- Post a double-entry journal. The sum of debits must equal the sum of credits; we validate and balance server-side before anything touches the ledger. Always send an `Idempotency-Key` so a retried request never double-posts. operationId: postJournal parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/JournalCreate' example: businessId: biz_9f2 narration: Office rent — November currency: NGN entries: - type: debit accountId: acc_rent amount: 25000000 - type: credit accountId: acc_cash amount: 25000000 responses: '201': description: Journal posted. content: application/json: schema: $ref: '#/components/schemas/Journal' example: id: jrnl_7x2a9 status: posted balanced: true businessId: biz_9f2 currency: NGN narration: Office rent — November entries: - type: debit accountId: acc_rent amount: 25000000 - type: credit accountId: acc_cash amount: 25000000 postedAt: '2026-11-08T09:24:11Z' '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '404': $ref: '#/components/responses/NotFound' '422': $ref: '#/components/responses/Unprocessable' components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false description: >- A unique key (e.g. a UUID) that makes a write safe to retry. Replaying the same key returns the original result instead of creating a duplicate. schema: type: string maxLength: 255 example: a1b2c3d4-0000-4000-8000-000000000000 schemas: JournalCreate: type: object required: - businessId - entries properties: businessId: type: string example: biz_9f2 narration: type: string example: Office rent — November currency: type: string description: ISO 4217 code; defaults to the business base currency. example: NGN date: type: string format: date description: Posting date; defaults to today. entries: type: array minItems: 2 description: At least two lines whose debits and credits balance. items: $ref: '#/components/schemas/JournalEntry' Journal: type: object required: - id - businessId - status - balanced - entries properties: id: type: string example: jrnl_7x2a9 businessId: type: string example: biz_9f2 status: type: string enum: - posted - reversed example: posted balanced: type: boolean example: true currency: type: string example: NGN narration: type: string example: Office rent — November entries: type: array items: $ref: '#/components/schemas/JournalEntry' postedAt: type: string format: date-time example: '2026-11-08T09:24:11Z' JournalEntry: type: object required: - type - accountId - amount properties: type: type: string enum: - debit - credit example: debit accountId: type: string example: acc_rent amount: type: integer description: >- Amount in the currency's minor unit (e.g. kobo, cents). Always positive. minimum: 1 example: 25000000 Error: type: object required: - error properties: error: type: object required: - type - message properties: type: type: string description: A stable, machine-readable error type. example: invalid_request message: type: string description: A human-readable explanation. example: businessId is required. code: type: string description: A dotted sub-code for finer handling. example: business.missing param: type: string description: The offending parameter, when applicable. responses: BadRequest: description: The request was malformed. content: application/json: schema: $ref: '#/components/schemas/Error' Unauthorized: description: Missing or invalid API key. content: application/json: schema: $ref: '#/components/schemas/Error' NotFound: description: The resource does not exist. content: application/json: schema: $ref: '#/components/schemas/Error' Unprocessable: description: >- The request was well-formed but could not be processed (e.g. a journal whose debits and credits do not balance). content: application/json: schema: $ref: '#/components/schemas/Error' example: error: type: unbalanced_journal message: Debits (25000000) do not equal credits (24000000). code: journal.unbalanced securitySchemes: bearerAuth: type: http scheme: bearer description: >- Authenticate with your secret API key as a bearer token: `Authorization: Bearer 3r_live_...`. Keys are issued per partner from the dashboard; use `3r_test_...` against the sandbox. Never expose a secret key in client-side code. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.