European Patent Office

Article 23

Citation: OJ EPO 2026, A23

Online publication date: 31.3.2026

EUROPEAN PATENT OFFICE

Information from the EPO

Definition of "DOCX" for filing with the European Patent Office (version 3) dated 25 March 2026

The present document supersedes the definition of "DOCX" for filing with the European Patent Office (version 2) dated 7 July 20251 with effect from its entry into force on 1 April 2026.

Office Open XML (DOCX OOXML)

1. General requirements

All documents in Office Open XML format (DOCX OOXML), which are represented by the file extension ".docx", must conform to the DOCX markup strict variant of OOXML specified in the "word processing" category of ISO/IEC 29500-1:2008.

In addition, they must fulfil the following requirements:

  1. Be in the format Office Open XML marked up according to the strict variant of OOXML for the category "word processing" (ISO/IEC 29500-1:2008)

  2. DOCX file must not be encrypted

  3. Page size must be either letter or A4

  4. Where applicable, in accordance with Rule 49(2) EPC and the decision of the President of the European Patent Office adopted thereunder,2 the font size 11 is recommended for plain text within the application document

  5. Where applicable, the headings and sections within the application document should adhere to the Common Application Format (CAF) standard (see wipo.int/pct/en/filing/caf.html) and use a paragraph style that adheres to the Office Open XML naming standards, as follows:

  • Titles of the main sections of the application as specified under "Application headings and sections" below

  • Description sub-sections as specified under "Application headings and sections" below

  • Claim lists as specified under "Application headings and sections" below

  • Figure lists as specified under "Application headings and sections" below (where applicable)

  • Reference numbers

  • Patent and non-patent citations

  • Bio-deposit

  • Citation list

  1. No hidden text

  2. No annotations (e.g. comments, ink annotations, etc.)

  3. No tracked changes

  4. The following OLE objects are supported:

  • ChemDraw.Document.6.0

  • MDLDrawOLE.MDLDrawObject.1

  • ISIS Server

  • Equation.3

  • Enhance.Map

  • Visio.Drawing.11

  • Equation.DSMT4

  • ChemWindow.Document

  • Origin50.Graph

  • PatXML.Image

  • Prism6.Document

  • ACD.ChemSketch.20

  • Visio.Drawing.15

  • Prism5.Document

  • ChemDraw.Document.4.5

  • SolidEdge.DraftDocument

  • Word.Picture.8

  1. Embedded images must be in TIFF, JPEG (JFIF) or PNG format

  2. Maximum allowable size for a single embedded image is 1 Mb

  3. No automatic updating of bookmarked or cross-referenced content, i.e. it is retrieved as submitted

  4. No text extraction from headers and footers

  5. No watermarks

  6. No content controls

  7. Typographical text highlighting effects are limited to the ones defined in the "application-body.dtd" (Appendix I of the Annex F of the Administrative Instructions under the PCT) (e.g. underlining, bold, italic, etc.)

  8. All text in the document must be typed using the following supported Unicode fonts:

  • Arial

  • Arial Black

  • Arial Narrow

  • Arial Rounded MT Bold

  • Arial Unicode MR Regular

  • Batang

  • Calibri

  • Cambria

  • Cambria Math

  • Courier New

  • Courier Regular

  • Georgia

  • MS Mincho

  • PMingLiU

  • SimSun

  • Symbol

  • Tahoma

  • Times New Roman

  • Trebuchet MS

  • Verdana

  1. No duplication of application headings

  2. No hyperlinks.

2. Application headings and sections

An application filed as a single DOCX file ("application body") must be divided by means of heading sections into different subject parts. The headings are defined as main sections (description, claims, abstract, drawings). The headings and sections of the application, including the order in which they appear, should follow the CAF guidelines (see example at wipo.int/pct/en/filing/caf_example.html).

An application filed in multiple DOCX files must reflect, at the beginning of each document, the respective heading as defined in section 2.1 (description, claims, abstract and, where applicable, drawings).

For an application written in English, the following applies:

2.1 Headings of the application body:

  • Description

  • Claims (mandatory)

  • Abstract (mandatory)

  • Drawings (where applicable)

Each heading of the application body (description, claims, abstract and, where applicable, drawings) must be at the top of a new page, separated either in a new section (page break) or separated by a page break, both functionalities being available in DOCX OOXML format.

2.2 Sections and sub-sections in a description (recommended):

  • Title of invention or Title

  • Technical field or Field

  • Background art or Background

  • Summary of invention or Summary

    • Technical problem

    • Solution to problem

    • Advantageous effects of invention

  • (Brief description of drawings)

  • Description of embodiments

    • Examples

  • Industrial applicability

  • Reference signs list

  • Reference to deposited biological material

  • (Sequence-listing free text)

  • Citation list

    • Patent literature

    • Non-patent literature

2.3 Numbering of claims

The set of claims must be numbered sequentially. It is recommended to use the automatic numbering function of the DOCX editor. If the claims are numbered manually, one of the following two formats should be used:

Claim 1.

Claim 2.

to Claim N.

or

[Claim 1]

[Claim 2]

to

[Claim N]

2.4 Drawings

Drawings (mandatory where drawings are present in the application and not filed separately in PDF in accordance with section 3):

The figures must be listed in numbered sequence, as follows:

Fig. 1

Fig. 2

to

Fig. N

3. Drawings filed separately in PDF

Any drawings may also be filed as a separate document in PDF instead of DOCX format.3 Drawings filed separately in PDF must comply with Annex F to the Administrative Instructions under the PCT.

4. Translations, amendments and documents filed for the purpose of identifying their basis

Sections 1, 2 and 3 apply mutatis mutandis to translations and documents replacing application documents in full or in part.

Sections 1(g) and 1(h) do not apply to documents filed for the purpose of identifying or explaining any amendments to the application documents.

5. Other documents

Section 1 applies mutatis mutandis to documents that are not application documents, with the exception of section 1(g) and 1(h).

  2. 2 See, currently, the decision of the President of the EPO dated 7 July 2025 on the presentation of application and other documents (OJ EPO 2025, A49).

  3. 3 See sections 1 and 2.4.