At the applicant's request and on payment of the prescribed fee, European patent applications (direct or Euro-PCT) and thus patents can be extended to European states for which an extension agreement with the EPO has become effective (extension states). The same applies to requests for validation in European or non-European states for which a validation agreement has entered into force (validation states).

The states for which such requests may currently be filed are listed below:

Bosnia and Herzegovina (BA)

since 1 December 2004

Montenegro (ME)

since 1 March 2010

The EPO's extension agreements with the Republic of Slovenia (entry into force: 1 March 1994), the Republic of Romania (15 October 1996), the Republic of Lithuania (5 July 1994), the Republic of Latvia (1 May 1995), the Republic of Croatia (1 April 2004), the Republic of North Macedonia (as the former Yugoslav Republic of Macedonia) (1 November 1997), Albania (1 February 1996) and the Republic of Serbia (1 November 2004) terminated when these countries acceded to the EPC with effect from 1 December 2002, 1 March 2003, 1 December 2004, 1 July 2005, 1 January 2008, 1 January 2009, 1 May 2010 and 1 October 2010 respectively. However, the extension system continues to apply to all European and international applications filed prior to those dates, and to all European patents granted in respect of such applications.

Morocco (MA)

since 1 March 2015

Republic of Moldova (MD)

since 1 November 2015

Tunisia (TN)

since 1 December 2017

Cambodia (KH)

since 1 March 2018

Extension and validation agreements are bilateral international treaties concluded between the European Patent Organisation and the state in question. Within the territory of the state concerned, the effects of a European patent application for which an extension or validation request has been filed, or of a European patent which has been validated in an extension or validation state, are based on national law. The provisions of the EPC, its Implementing Regulations and the Rules relating to Fees do not apply to the extension and validation systems, unless and only to the extent that those provisions are referred to by the applicable national law. Thus, the EPC provisions concerning applicants' legal remedies and appeals do not apply in respect of any action taken by the EPO under the extension or validation procedure (see e.g. J 14/00, J 4/05 and J 22/10), e.g. where the extension or validation fee has not been paid within the applicable time limit indicated (A‑III, 12.2). Similarly, no different claims, description or drawings are acceptable in respect of extension or validation states (see H‑III, 4.4), as Rule 138 EPC does not apply to the extension and validation systems.

A request for extension to or validation for the above-mentioned states is deemed to be made with any European application filed after entry into force and, as to the former, before the termination of the respective extension agreements. This applies also to Euro-PCT applications provided that the EPO has been designated for a European patent and the extension or validation state has been designated for a national patent in the international application. The request is deemed withdrawn if the extension or validation fee is not paid within the prescribed time limit (see A‑III, 12.2). It is by paying the extension or validation fee that the applicant decides to extend the application to an extension state or validate it in a validation state. The declaration in the appropriate section of the request for grant form (EPO Form 1001) or of EPO Form 1200 for entry into the European phase before the EPO, where the applicant is asked to state whether the extension or validation fee is intended to be paid, is merely for information purposes and intended to assist in recording fee payments.

A request for extension or validation in respect of a divisional application (see A‑IV, 1) is deemed to be made only if the respective request is still effective in the parent application when the divisional application is filed.