---
title: Subjects and identifiers
description: One subject per IČO with all its registrations, how identifiers are matched, and the quirks of the source data.
---

## One subject, several registrations

In RPO, one IČO can have **several records**: a sole trader has one per source register (for example the Trade
Register and the register of financial agents), and an old company can have closed branch records. About 22 600
IČOs have more than one active record.

Accquix Register treats them as **one subject**:

- the lookup returns `identity.registrations[]`, one entry per record, each with its register, office, number,
  the name in that record, and whether it is active;
- the **display name** comes from the Commercial Register or Trade Register record, else from the most recently
  changed record;
- **every official name is searchable**, so a sole trader is found under any of the names they use;
- a record without a valid IČO keeps its own identity, keyed by its RPO id.

## Identifiers are matched exactly

| Typed | Recognised as | Example |
| --- | --- | --- |
| 8 digits | IČO | `99900001` |
| 10 digits | DIČ | `2099900001` |
| `SK` + 10 digits | IČ DPH | `SK2099900001` |

Spaces are ignored and `sk` is accepted. Identifiers are **never matched fuzzily**: an IČO that differs by one digit
is another, real company.

:::warning[The IČO check digit is a warning only]
The last digit of an IČO is a mod-11 check digit. In the real data, 778 IČOs fail it, 16 of them active.
So a failing IČO is never rejected: when it exists in RPO it is returned, and `identity.icoChecksumValid` says
`false`.
:::

**An IČ DPH is not a unique key.** The members of a VAT group (§4b) share one IČ DPH, so a lookup by IČ DPH can
return several subjects.

## What the source data looks like

These facts, found in the real files, shape how the register reads them:

- about 6 600 RPO records carry a text placeholder instead of an IČO; they are treated as having no IČO;
- some IČOs in the Financial Administration lists are not 8 digits (mostly 12-digit numbers of another kind);
- RPO writes the PSČ both as `83237` and `811 06`; the register returns `NNN NN`;
- when a subject is terminated, RPO closes every attribute; the register then shows the last valid value;
- the special VAT scheme list can have several periods with the same start date for one subject.