1. Continuity: Pre-accession procedures will continue up to accession. A smooth and rapid transition from there into EU procedures should be reached.
2. Rule of law: Existing EC legislation will fully apply to new Member States as of date of accession.
3. No new procedures: Existing EU frameworks and procedures are necessary and sufficient to cater also for the specific economic and economic policy challenges of new Member States.
4. Equal treatment: EU procedures will be applied, by granting equal treatment to all Member States since the time of accession. Precedents from previous accessions can provide guidance, but do not necessarily create an obligation.
5. Information and consultation: Future Member States will be fully informed and consulted, where appropriate, on all aspects related to their integration in the EU surveillance procedure.

These principles were applied and are still applied to all Member States. By contrast to the 10 countries that joined the EU in 2004, in the case of Romania and Bulgaria some changes might come up due to:

• different months of accession during the year (1 January instead of 1 May);
• changed EU procedures;
• late decision on accession date.

Source: EC website