---
title: Freshness and certainty
description: Section states, stale data, when the API says "not found", and section versions.
---

A mirror can be behind. Accquix Register never turns "I do not know" into "it does not exist".

## Section states

Every lookup section carries a `state`:

| State | Meaning |
| --- | --- |
| <State is="present" /> | The source has a row for this subject. |
| <State is="absent" /> | The source is **fresh** and has no row. This is a fact as of the source's date. |
| <State is="unknown" /> | The source was never published, or it is stale. The register does not know. |

Values derived from a section follow the same rule. For example `vat.payer` is `true` or `false` only from a fresh
list, and `null` otherwise.

## Fresh and stale

Each source carries the date the agency stamped on its data (`asOf`). A source is **stale** when that date is older
than:

| Source | Maximum age |
| --- | --- |
| RPO | 3 days |
| Financial Administration lists | 2 days |
| Reliability index (`ds_iz_ran`) | 14 days (it is refreshed irregularly) |

A stale section is still returned, with `source.stale: true`. `GET /v1/sources` shows every source's state and date.

## "Not found" only when it is true

| Situation | Answer |
| --- | --- |
| Every consulted source is fresh and none has the identifier | `404 not_found` |
| Not found, but a consulted source is stale | `503 unavailable`, reason `source_stale` |
| The mirror is still being built | `503 unavailable`, reason `bootstrapping` |
| Found, some sections stale | `200`, those sections flagged `stale` |

Treat `503` and `unknown` as "unknown", never as "not found". An outage of the register must not block your
workflow.

## Versions

Every section has `source.version`: a hash of its content. A rebuild from the sources yields the same versions, so a
consumer can store the version with its copy and compare it later to see what changed. See
[Change detection](/api/changes).

## No history

The register keeps the current state, when a row last changed (`changedAt`), and when it disappeared from a list
(`absent_since`). A disappearance is an observation, never a legal date: for example, the Financial Administration
publishes no VAT cancellation date, and a payer that loses its registration simply leaves the list.