# Responsible declaration

English rendering of Negative Epsilon SL's responsible declaration for FiscalRail version 1 under Article 15 of Order HAC/1177/2024.

The [Spanish declaration](/es/docs/tax-regimes/spain/responsible-declaration) is the authoritative declaration subscribed by Negative Epsilon SL. This page is an English rendering for convenience.

**1.a) Name of the invoicing system covered by this responsible declaration**

FiscalRail.

**1.b) Identifying product code**

`WH`.

**1.c) Full identifier of the specific version**

Version `1`.

**1.d) Hardware and software components, their purpose and principal functions**

FiscalRail is a software-as-a-service (SaaS) application that runs on a public cloud and provides a web dashboard and an API.

**1.e) Whether the system was produced to operate exclusively as VERI*FACTU for regulatory purposes**

Yes. For taxpayers subject to the regulation approved by Royal Decree 1007/2023, FiscalRail version 1 operates only in VERI*FACTU mode. It does not implement the alternative local-record-retention mode for those taxpayers.

**1.f) Whether several taxpayers can use the system, or one user can use it to support several taxpayers**

Yes. FiscalRail is multi-company and can serve several taxpayers. Data, series, installations and billing-record chains are segregated by account.

**1.g) Signature types used for billing and event records when the system is not used as VERI*FACTU**

Not applicable. FiscalRail version 1 operates exclusively as VERI*FACTU for taxpayers subject to the regulation.

**1.h) Legal name of the system producer**

Negative Epsilon SL.

**1.i) Spanish tax identification number of the system producer**

`B02850360`.

**1.j) Full postal contact address of the system producer**

Paseo de la Castellana 194, 28046 Madrid, Spain.

**1.k) Declaration of conformity with the applicable rules**

Negative Epsilon SL declares that FiscalRail version 1 complies with Article 29.2.j of Spanish General Taxation Law 58/2003 of 17 December; the invoicing-system and billing-record standardization regulation approved by Royal Decree 1007/2023 of 5 December; Order HAC/1177/2024 of 17 October; and the implementing specifications published at the AEAT electronic office.

**1.l) Date and place where the responsible declaration was subscribed**

16 August 2026. Madrid, Spain.

## Legal basis

The Spanish declaration follows the content and order required by [Article 15 of Order HAC/1177/2024](https://www.boe.es/buscar/act.php?id=BOE-A-2024-22138#a15). The AEAT also publishes [official responsible-declaration examples](https://sede.agenciatributaria.gob.es/static_files/Sede/Tema/IVA/Verifactu/EjemplosDeclaracionResponsable%28V0.5.1%29.pdf).