DOCX Filing at the European Patent Office – Use it or not?

Some recommendations from epi‘s Online Communication Committee (OCC) and epi‘s European Patent Practice Committee (EPPC)

According to the Notice of the European Patent Office dated March 25, 2026 (OJ EPO 2026, A22, available here), the European Patent Office has, effective April 1, 2026, authorized a new file format for filing patent applications and other documents: DOCX.

epi, the Institute of Professional Representatives before the European Patent Office, in particular epi‘s Online Communication Committee (OCC) and epi’s European Patent Practice Committee (EPPC), have identified at least the following issues to be considered when using DOCX in EPO filings:

1. Careful Review of Specifications

Make sure you read and follow the EPO’s detailed specification and guidance to minimize the risk of loss of rights. Don’t just assume the DOCX you edited with your client can be uploaded without risk.

It is not sufficient to edit a DOCX document with the client and then file it. The EPO’s exact technical specification must be reviewed before filing. Many standard settings in Microsoft Word do not meet the EPO’s specification.

The EPO’s detailed DOCX specification can be found here.

2. Avoid fonts which are not explicitly listed as being allowed in the specification

For example, the EPO’s list of acceptable formats for DOCX filing indicated in the EPO’s above-mentioned specification excludes APTOS - the new Microsoft 365 default font.

APTOS has recently been set by Microsoft as its default font in Microsoft 365 (Word, Excel, etc.). Organizations which use Microsoft’s default settings will likely save their DOCX files with APTOS font. This is a critical point because it is not clear whether it is compliant with the present EPO’s requirements for DOCX format specification.

3. Dynamic and Increasing Complexity

Be aware that your next filing may have more complex formatting, formulae and symbols etc. than the one you did before.

This addresses a fundamental risk: you may file a simple DOCX document successfully and believe you have mastered the format. But the next application with formulas, graphics, or more complex formatting may cause unforeseen problems. This requires continuous attention and review, not mere routine.

4. Use PDF Backup Copy

Use the facility to upload a PDF back-up copy, just in case something gets lost in conversion.

The EPO provides the ability to file a PDF backup copy. This should not be regarded as an optional luxury feature, but as a necessary quality assurance tool. In cases of technical problems or conversion errors, the PDF backup copy can serve as evidence.

5. Compatibility with Other Systems

Understand that a file compatible with the EPO specification is not automatically compatible with PCT and/or foreign requirements.

A document that meets the EPO’s specification is not automatically suitable for PCT filings or foreign offices. Those filing internationally must review the requirements of all affected jurisdictions and may need to maintain different versions of the same document.

6. Workflow Design and Training

Design your workflows and guardrails thoughtfully; be vigilant for lost content. Attend to training of all involved.

This is a recommendation for law firms and companies: it is not enough to upload a DOCX file. Workflows need to be rethought. All employees involved (attorneys, paralegals, assistants) must be trained. Controls and safeguards must be implemented to ensure that content is not lost.

7. Gradual Introduction

Consider trying DOCX filing for situations where errors are easier to correct than in, for example, a critical priority filing.

This recommends a pragmatic, risk-averse approach: DOCX filings should initially be tested for cases where errors are easy to correct (e.g., subsequent filings, non-critical submissions). Critical submissions should initially be filed in proven formats (PDF) until experience with DOCX is gained.

Recommendations for Your Organization

1. Don’t try to switch fast: start with DOCX filings early for less critical submissions. Test the format when the deadline allows for corrections or re-filings. Only once you are confident you master the format and process should you use it as a standard also for critical filings.

2. Provide training: everyone who creates or reviews DOCX files should be trained. They need to know the EPO’s specification.

3. Create checklists: develop internal checklists to ensure before filing that each DOCX document meets the EPO’s specification.

4. Use the option to file PDF backup copies: it doesn’t cost much and protects you in an emergency.

5. Create templates: create Word templates with the correct fonts, formatting, and sizes. This saves everybody in your organization a lot of headache resolving errors.

6. Respect international requirements: if you operate internationally, check whether your DOCX files are also compatible with PCT or foreign office requirements.

Conclusion

The ability to file DOCX documents at the EPO is a good thing. It simplifies some work steps and saves the conversion to PDF.

But it is not as simple as “just open Word and start writing.” The EPO has defined exact technical requirements. Microsoft Word does not meet these as default. If you are not careful, you may run into significant trouble.

IMPORTANT: Understand that not every Word document is automatically EPO-compliant. You must actively check and ensure that your DOCX documents meet the EPO’s specification. This is an additional responsibility that you should not underestimate.
In addition to the issues listed above, there might be further risks.

Now that you are aware of the requirements and risks, start testing and adopting the new format timely and proceed diligently; you will be able to use DOCX filings successfully in no time!