Headless · MCP-native · self-hostable
The ledger of record your agents may write to — and your auditors can verify.
Ledgerbook AI is the headless, MCP-native accounting data layer: one immutable, bitemporal book of record for every system you run — deployed in your own infrastructure, correctable only by provable, attributable entries.
- chain-hashed by default
- verify offline
- air-gap installable
- fiat, exact-decimal money
Phase legend: PH-1 shipped now · Roadmap arrives with PH-2. Labels are always present — colour is never the only signal.
Proof primitives
OCEL 2.1
audit-export format, schema-validated in CI · FR-905
T0/T1
materiality tiers evaluated server-side · FR-217
ISO-4217
fiat only; integer minor units, no floats anywhere · FR-107
0
models in the posting path — agents interact via MCP · NG-4
The intelligence layer is arriving faster than the data layer can support it.
Three conditions every finance stack shares, and no closed application fixes from the inside.
Truth is fragmented
Balances live across ERPs, banks, billers and spreadsheets. Each system answers a different question in a different vocabulary, and the consolidation sink is a spreadsheet.
Provisional numbers have nowhere to live
Teams either post early or report late. Either way the evidence of what was believed, and when, is destroyed before anyone asks.
Agent writes are ungoverned
Agents are being handed write access with no per-action provenance, no materiality gate and no content-bound approval. That is a control failure waiting for an audit.
One record you can prove. Writes you can govern. A ledger you can own.
PH-1
One record you can prove
Every Final entry is chain-hashed, and the chain is on by default. Corrections are typed reversing, adjusting or restating entries — never edits. Every read answers as-of: the balance at a date, and the balance as we believed at a past instant.
Immutability & verification →PH-1 · T0/T1
Writes you can govern
Agents propose; they cannot approve, finalize or correct — enforced at the credential, not the prompt. Approvals are content-hash-bound, and any edit voids a pending approval. Every mutation is a provenanced event.
MCP server & governance →PH-1
A ledger you can own
Self-hosted and air-gapped is a first-class deployment: one process on a VM or a bare-metal HA cluster, an offline bundle with zero egress. No proprietary formats — OCEL 2.1 and open interfaces. Planning consumption Roadmap arrives in PH-2.
Self-hosted & air-gap →One object, one identity — never an edit
Provisional and Final are the public lifecycle terms. Corrections are new, typed entries; the original stays exactly where it was.
-
Provisional T0 · entry.created
Every material edit appends an immutable revision — actor, timestamp, content hash — to the same entry object. Nothing is overwritten.
-
Final one-way · entry.finalized
Finalization seals that same object: postings become immutable, the entry id never changes, and the chain hash is on by default.
-
Correction entry.reversed · entry.corrected
Later economic changes arrive as typed reversing, adjusting or restating entries, linked to the original. The mistake and the fix both stay visible.
-
Period states & T2/T3 tiers
Roadmap
Period states, close gates and the higher approval tiers are ledger-native by design and arrive with PH-2.
Read the ledger the way your agents will
MCP is a first-class surface with the same semantics and error taxonomy as HTTP — and it works air-gapped with your own local model. Balances come back with their chain position attached.
# JSON-RPC 2.0 tool call — effective time and knowledge time on every read
→ tools/call get_balance
{
"ledger": "grp-eu",
"book": "group_ifrs",
"scenario": "actual",
"account": "1000",
"as_of": "2026-08-31", # effective time
"as_believed": "2026-09-19T09:41:07Z" # knowledge time
}
← 200 { "balance_minor": 18425000, "currency": "EUR",
"status": "final", "ledger_seq": 841223 }Pick your entry point
Six ways into the same ledger. Each one starts from the job, not the feature list.
Embed a real ledger — per tenant, without becoming an accounting company
Invariants below you: double-entry, immutability and governance as an API and an MCP server. Per-tenant isolation, validate-before-commit, and test-class credentials that can never write to production.
Per-tenant isolation FR-126 · validate-before-commit FR-116 · test credentials FR-807 · PH-1
Platform builders →Zero-day truth without weakening the audit trail
Provisional numbers today, provable numbers forever. One verifiable book of record across the estate, with as-of answers, typed corrections and a data-quality envelope on every disclosure.
Provisional bridge FR-230/232 · data-quality envelope FR-230 · PH-1
Finance teams →Your agents propose. Your policy approves. The chain proves it.
Read and propose against one ledger with scenario and status filters; never posting rights, always attribution. Proposals run the materiality gate server-side, and every call appends a provenance event.
Proposal-only credentials FR-220 · hash-bound approvals FR-215 · PH-1; full MCP tool surface Roadmap
AI-agent platforms →Plan on the same ledger as actuals Roadmap
Give your planning module one real ledger: scenario-tagged postings and as-of reads for actual, provisional and planned — no ETL, no copied actuals. Scenario registry and filters are consumable today; delta inheritance and variance runs arrive in PH-2.
Scenario registry FR-301/304 · filters FR-342 · PH-1; delta ops FR-310–334 Roadmap
Planning vendors →Two more families to walk:
Comparisons, on the record
Verifiable facts only. Every table is dated, every claim links its source, and “where they win” is mandatory — because an honest table is the only one worth citing.
| Comparison | Axis | Status | Page |
|---|---|---|---|
| Ledgerbook vs Formance | Hash-chained bi-temporal log, MIT-licensed open-source core, self-host proportions | 2026-09-19 | Compare → |
| Ledgerbook vs Blnk | OSS Go fintech ledger; chain off by default, balances mutate in place | 2026-09-19 | Compare → |
| Build vs buy | What the free option costs when audit evidence is the requirement | in preparation | — |
What Ledgerbook is not
- Not an ERP, and not a replacement for one — it is the ledger beneath them (NG-2).
- No UI, no close workflows, no AP/AR: your application renders it; the ledger proves it (NG-1).
- No money movement — payment systems are ingestion sources (NG-3).
- No model in the core; agents reach it over MCP (NG-4). Fiat ISO-4217 money only (FR-107).
Get early access
The design-partner programme is open. Named partners only — we publish no placeholder logos.
Design-partner programme open — consented names appear here at launch. Pre-launch, this wall stays empty by policy: no invented logos, no implied endorsements.