> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cast.digitalfinancehq.com/llms.txt
> Use this file to discover all available pages before exploring further.

# The ledger is no longer the system of record

> The event log is.

The general ledger has been the system of record for five hundred years. CAST inverts that: the **event log** is the system of record, and the ledger is a projection of it.

## The inversion

In conventional accounting, the ledger is authoritative. Everything else — supporting documents, approvals, correspondence — exists to justify the entries in it. When a question arises, you start from the ledger entry and work backward, reconstructing the context that produced it.

CAST reverses the dependency. The authoritative artifact is the append-only event log. Postings are *derived* from completed work orders, which are derived from events. The ledger is no longer the thing you reconstruct *toward* — it is a thing you *project from* the events that already hold the truth.

<Note>
  If every table but the event log were deleted and the log replayed, every posting would reconstruct exactly. The ledger is a view, not the source.
</Note>

## Why this matters

| Question                | Ledger-first answer               | Event-log-first answer         |
| ----------------------- | --------------------------------- | ------------------------------ |
| Who approved this?      | Reconstruct from email and memory | Read the decision event        |
| What policy applied?    | Infer from the date               | Read the pinned policy version |
| Has it been altered?    | Hard to prove                     | Verify the lineage hash        |
| Did both parties agree? | No record of the counterparty     | Read the bilateral event       |

## Intellectual lineage

This is not invented from scratch. It builds on **Sorter's events theory** of accounting — the idea that the basic data of accounting should be events, not pre-aggregated balances — and on **Ijiri's triple-entry** bookkeeping, given a bilateral, cryptographically bound form. CAST is the application of these ideas to commercial payments at the moment AI makes verification the scarce resource.

<Card title="Deterministic commerce" icon="ban" href="/foundations/deterministic-commerce">
  The consequence: reconciliation should not exist.
</Card>