---
title: "CAO.A.055 Maintenance data and work orders — Part-CAO · Avioverse"
description: "The CAO shall hold and use applicable current maintenance data specified in point M.A.401 of Annex I (Part-M) or in point ML.A.401 of Annex Vb (Part-ML)…"
url: "https://avioverse.aero/regulations/easa/continuing-airworthiness/part-cao/section-a-organisation-requirements/cao-a-055"
---

# CAO.A.055 Maintenance data and work orders

Annex Vd (Part-CAO) · Regulation (EU) No 1321/2014 · EAR revision 2 Sep 2025

Official sources: [EASA Easy Access Rules (opens in a new tab)](https://www.easa.europa.eu/en/document-library/easy-access-rules/easy-access-rules-continuing-airworthiness) · [EUR-Lex 2014/1321 (opens in a new tab)](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014R1321)

IR Implementing rule

## CAO.A.055 Maintenance data and work orders

(a) The CAO shall hold and use applicable current [maintenance](https://avioverse.aero/glossary/easa/maintenance) data specified in point M.A.401 of Annex I (Part-M) or in point ML.A.401 of Annex Vb (Part-ML), as applicable, in the performance of maintenance, including modifications and repairs. However, in the case of customer-provided maintenance data, it shall only be required to hold such data when the work is in progress.

(b) Before the commencement of maintenance, a written work order shall be agreed between the CAO and the person or [organisation](https://avioverse.aero/glossary/easa/organisation) requesting maintenance, in a manner that clearly establishes the maintenance to be carried out.

IR · CAO.A.055 — Regulation (EU) No 1321/2014 · Regulation (EU) 2019/1383 · Continuing Airworthiness Easy Access Rules · EAR revision 2 Sep 2025

AMC Acceptable means of compliance

## AMC1 CAO.A.055 Maintenance data and work orders

It is not required to continuously hold all the [maintenance](https://avioverse.aero/glossary/easa/maintenance) data. It is acceptable to have a procedure to ensure that the specific maintenance data required for a particular maintenance activity will be available before that maintenance takes place.

AMC · AMC1 CAO.A.055 — Regulation (EU) No 1321/2014 · ED Decision 2020/002/R · Continuing Airworthiness Easy Access Rules · EAR revision 2 Sep 2025

[All rules in SECTION A — ORGANISATION REQUIREMENTS](https://avioverse.aero/regulations/easa/continuing-airworthiness/part-cao/section-a-organisation-requirements)

Consolidated from the EASA Easy Access Rules (revision 2 Sep 2025, extracted 2 Nov 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.