HEADLESS · API-ONLY · APPEND-ONLY

Ledger17

Double-entry bookkeeping as an API.

Ledger17 is a headless ledger: no screens, no workflows — a command API records immutable, balanced transactions and a query API serves balances, subledgers and the live journal. Your systems post the facts; the ledger keeps the books.

rocket_launchGet started menu_bookDocumentation

Built on CQRS and event sourcing. Writes append immutable events; reads hit pre-calculated views, so queries stay fast at any ledger size.

ONE REQUEST, ONE BALANCED BLOCK

Post a transaction. Everything else is enforced.

Amounts are integer minor units. Every block must balance — the ledger refuses anything else.

POST /ledger/v1/transactions 201 Created

$ curl -X POST https://api.example.com/ledger/v1/transactions \
  -H "Content-Type: application/json" \
  -H "X-Tenant-ID: org-84120557" \
  -H "X-Idempotency-Key: inv-2026-0042" \
  -d '[{
    "name": "Sales invoice #42",
    "transactionDate": "2026-07-01",
    "unit": "EUR",
    "entries": [
      { "accountReference": "1500-receivables",
        "entryType": "DEBIT",  "amountMinorUnits": 125000,
        "dimensions": { "CUSTOMER": "cust-001" } },
      { "accountReference": "3000-sales",
        "entryType": "CREDIT", "amountMinorUnits": 100000 },
      { "accountReference": "2700-vat-out",
        "entryType": "CREDIT", "amountMinorUnits": 25000 }
    ]
  }]'

transaction block a3f9…c217

1500-receivables	DEBIT	1,250.00
3000-sales	CREDIT	1,000.00
2700-vat-out	CREDIT	250.00
Σ debits = Σ credits		✓ balanced

Blocks that don't balance exactly are rejected with 400 UNBALANCED_TRANSACTION. Once accepted, a block is immutable — corrections are new, compensating blocks.

WHY HEADLESS

Accounting guarantees, delivered over HTTP

history_edu

Append-only, immutable

Transactions are events, stored forever. No updates, no deletes — corrections are compensating reversals, so the audit trail is the database.

balance

Double-entry, enforced

Every transaction block must balance: Σ debits = Σ credits, exactly — integer arithmetic, no rounding. Unbalanced writes are rejected before they touch the books.

bolt

Fast, pre-calculated reads

Balances are aggregated as transactions post, not when you ask. Queries are lookups, not scans — response times stay flat as the books grow.

fingerprint

Idempotent writes

Every write carries an X-Idempotency-Key. Retry as hard as you like — the same key can never post twice.

account_tree

Dimensions & subledgers

Tag entries with CUSTOMER, SUPPLIER, PROJECT and more. Rollups are pre-computed for every dimension in parallel; each query filters on one.

podcasts

Live event stream

Subscribe to the journal over WebSocket and follow every posted block in real time — from any sequence number you choose.

AGENTS & INTEGRATIONS

Built for software — human optional

The same ledger, three ways in: an MCP server for AI assistants, API keys for unattended systems, and an admin console for your tenant.

smart_toy

MCP server for AI agents

Connect Claude or any MCP client to mcp.ledger17.com and the ledger becomes tools: balances, subledgers, reports — and balanced writes. The caller’s own permissions apply; the admin API is deliberately absent.

AI agent docs chevron_right

vpn_key

API keys for integrations

Unattended systems authenticate with an API key bound to one tenant, scoped to exactly the permissions the integration needs — read:ledger for a dashboard, write:ledger for a posting system.

API key docs chevron_right

admin_panel_settings

Admin console

Manage your tenant, subscription and API keys at admin.ledger17.com. Everything else stays headless — the console administers access; your systems and agents keep the books.

Get started chevron_right

TWO SERVICES, ONE LEDGER

Command writes. Query reads.

All endpoints live under /ledger/v1. Tenant scoping via X-Tenant-ID, OIDC bearer tokens in production.

south_westCommand API :8080

Record transaction blocks, submit business events, reverse mistakes. Accepts facts; derives and validates entries via domain rule sets.

POST /ledger/v1/transactions record balanced blocks
POST /ledger/v1/transactions/{id}/corrections compensating reversal
POST /ledger/v1/events submit a business event
POST /ledger/v1/events/batch bulk import (up to 10 000)
GET /ledger/v1/events inquire submitted events

Command API reference chevron_right

north_eastQuery API :8081

Read the books: balances, transaction lines, subledger rollups, party exposure and the live journal — served from pre-aggregated views, fast at any size.

GET /ledger/v1/balances account balance for a period
GET /ledger/v1/transactions transaction lines
GET /ledger/v1/subledger subledger rollup by dimension
GET /ledger/v1/parties/{partyId}/exposure net exposure per party
WS /ledger/v1/events live journal stream

Query API reference chevron_right