Implementation of European Standards - ENs not corresponding to national standards on a one-to-one basis

This page outlines the CEN policy on the national implementation of European Standards (EN) not corresponding directly to existing national standards on a one-to-one basis.


All CEN members are obliged to implement ENs as national standards without any modification and to withdraw any conflicting national standards. However, when fulfilling these obligations, CEN members are often faced with the problem that the scope of the EN does not fully cover the scope of existing national standards. There may be good reasons why remaining aspects dealt with by those national standards are still needed by the market (e.g. national traditions that cannot be standardized at European level).


The basic rule should be to avoid the creation (or recognition) of barriers to trade.
All CEN members have to be aware that any additional national requirements may adversely affect trade within the European market. Therefore, all CEN members are obliged to ensure that their standardization activities at national level do not result in conflicting national standards, which might be considered as discriminatory against foreign suppliers. All national activities shall be identified in the member’s work programme, as required through Regulation 1025/2012 on European Standardization.


All CEN members having the intention to publish national supplements to existing ENs shall notify this intention to the responsible Technical Committee (TC) as early as possible. This notification should include a description of the envisaged technical content of the national supplement. Furthermore, all background information should be given to explain why these additional aspects cannot be standardized at European level.
The responsible CEN/TC should examine the notification and provided information and has to decide:

  • whether the EN should be revised in order to integrate the suggested supplements;
  • whether the supplements should be considered as new work at European level;
  • whether the suggested national supplements could be considered as potential barriers to trade.

All cases of potential barriers to trade should be brought to the attention of the Technical Board (BT).


Before starting technical discussions on new work, the responsible CEN/TC should invite all CEN members to describe the aspects that should be covered by the future EN. Furthermore, the CEN Members should be invited to suggest a possible scope and application field.

At this stage, it might be useful to identify the existing national standards and to notify all aspects that are covered by these national standards. It is the task of the CEN members to inform the TC Secretary accordingly. The TC Secretary should prepare a summary of the received information.

The scope of an EN reflects precisely what is covered (and where appropriate, what is not covered) by the EN. It is essential that the TC gives clear instructions to the responsible Working Group (WG). If, during the technical discussions, it becomes clear that these instructions do not cover all the needs of the CEN members, the WG shall inform the TC accordingly. The TC has to decide whether the scope and field of application could be enlarged.

All CEN members should check whether the scope and application field of the existing national standards that will have to be withdrawn due to the future implementation of an EN under preparation are covered by the future EN. This should be done as early as possible and in any case no later than the CEN Enquiry stage.

If any 'necessary' aspect at national level is missing in the future EN, the CEN member should request the responsible TC to include this aspect in the EN. If the TC does not agree to this request, the aspect shall be excluded from the scope of the EN. However, when taking such a decision, the TC should consider possible options that might solve the problem. Such options may include the specification of different classes within an EN (e.g. different dimensions or other different characteristics used at national level).

In some cases, a longer transitional period might contribute to finding a solution. The TC should also take into account the instructions concerning (potential) technical diversity within ENs.

If, after careful consideration of the request, the TC decides to exclude one or more aspects from the scope and application field of the future EN, the CEN member is free to publish the additional aspects as national standards. However, the CEN member has to ensure that this national standard is not in conflict with the aims of European standardization and will not create barriers to trade.


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