---
title: "21.A.804 Identification of parts, appliances, and control and monitoring unit (CMU) components — Annex I, Initial Airworthiness · Avioverse"
description: "Each part or appliance which is eligible for installation in a type-certified product, and each CMU component which is eligible for installation in a CMU…"
url: "https://avioverse.aero/regulations/easa/initial-airworthiness/annex-i/section-a-technical-requirements/21-a-804"
---

# 21.A.804 Identification of parts, appliances, and control and monitoring unit (CMU) components

Annex I · Regulation (EU) No 748/2012 · EAR revision 27 Nov 2025

IR Implementing rule

## 21.A.804 Identification of parts, appliances, and control and monitoring unit (CMU) components

(a) Each part or appliance which is eligible for installation in a type-certified product, and each CMU component which is eligible for installation in a CMU certified in accordance with this Annex I, shall be permanently and legibly marked with:

1\. a name, trademark, or symbol identifying the manufacturer in a manner identified by the applicable design data;

2\. the part number, as defined in the applicable design data; and

3\. the letters ‘[EPA](https://avioverse.aero/glossary/easa/epa)’:

(i) for parts or appliances produced in accordance with approved design data that does not belong to the type-certificate holder of the related product, except for [ETSO](https://avioverse.aero/glossary/easa/etso) articles and for parts and appliances covered under point 21.A.307(b);

(ii) for CMU components produced in accordance with approved design data that does not belong to the type-certificate holder of the related CMU, or to the UA type-certificate holder when the CMU is certified as part of the UA, except for ETSO CMU components and CMU components covered under point 21.A.308(b).

(b) By way of derogation from point (a), if the Agency agrees that a part, appliance or a CMU component is too small, or that it is otherwise impractical to mark a part, appliance or a CMU component with any of the information required by point (a), the authorised release document that accompanies the part, appliance or the CMU component or its container shall include the information that could not be marked on the part, appliance or CMU component.

IR · 21.A.804 — Regulation (EU) No 748/2012 · Regulation (EU) 2024/1108 · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

GM Guidance material

## GM 21.A.804(a)(1) Identification of parts and appliances

It is not the intent of 21.A.804(a)(1) to introduce an obligation for a production organisation (manufacturer) to mark new parts or appliances with information which is not identified by the design approval holder. Therefore, the physical marking of parts and appliances is only required when established by the design approval (TC, STC, [ETSO](https://avioverse.aero/glossary/easa/etso), repair, change) holder.

For designs (TC, STC, ETSO, repair, change) approved after 28 December 2009 (the date of entry into force of Commission Regulation (EC) No 1194/2009), the design approval holder is required to identify to the manufacturer how the marking in accordance with 21.A.804(a)(1) should be done. This can be limited to identifying a marking field, possible depth and/or means etc., without prescribing the actual text or symbols to be used.

GM · GM 21.A.804(a)(1) — Regulation (EU) No 748/2012 · ED Decision 2012/020/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

GM Guidance material

## GM1 21.A.804(a)(3) Identification of parts and appliances

EUROPEAN PARTS APPROVAL ([EPA](https://avioverse.aero/glossary/easa/epa)) MARKING FOR REPAIR PARTS

The EPA marking only applies to the parts, specifically designed or modified for the repair, to be incorporated as part of the repair design. If the repair scheme does not require the addition of any new parts or the use of modified parts, there is no need to mark the repaired part with the letters ‘EPA’.

GM · GM1 21.A.804(a)(3) — Regulation (EU) No 748/2012 · ED Decision 2021/001/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

AMC Acceptable means of compliance

## AMC1 21.A.804(b) Identification of parts and appliances

EASA AGREEMENT FOR THE DESIGN APPROVAL HOLDER TO DEROGATE FROM POINT 21.A.804(a)

A design approval holder may apply point 21.A.804(a) or make use of the derogation defined in point 21.A.804(b) by clarifying, in the relevant procedures, the conditions (e.g. the minimum dimensions of a (flat) area on a part suitable for marking) in which the marking on the part may be completely or partially omitted. This can also be supported by examples of parts or cases when certain parts do not have to be marked.

In such cases, the relevant design data (e.g. drawings) should specify the contents and location of the information that could not be marked on the part (i.e. the information to be provided in the authorised release document or on the container).

AMC · AMC1 21.A.804(b) — Regulation (EU) No 748/2012 · ED Decision 2021/001/R · Initial Airworthiness Easy Access Rules · EAR revision 27 Nov 2025

[All rules in SECTION A — TECHNICAL REQUIREMENTS](https://avioverse.aero/regulations/easa/initial-airworthiness/annex-i/section-a-technical-requirements)

Consolidated from the EASA Easy Access Rules (revision 27 Nov 2025, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.