The EPO is an independent supranational organization and has nothing to do with the European Union. However, within the implementation of the unitary patent system, no separate "EU Patent Office" will be established, but the already existing European Patent Office will be used. This is a big difference to the application and granting of EU trade marks and EU designs. For this purpose, a separate EU authority was created with the EUIPO in Alicante/Spain.
Before a unitary patent can be registered, a European patent must first be obtained in accordance with the European Patent Convention (EPC). When filing the application, one does not yet have to decide whether they want a unitary patent or validate the patent later nationally in the conventional way. Only after the grant decision one has to notify the EPO where and how they want to validate. In order to obtain a unitary patent, a "request for unitary effect" must be filed with the EPO within one month after publication of the notice of grant.
If one does not wish to do this, they just make a cross - as before - with the individual states. Then they get a conventional EP patent, which is validated only in the corresponding states. It is also possible to combine the unitary patent with an additional validation in EPC contracting states, as long as these states are not EU states (e.g. Switzerland) or do not participate in the unitary patent system (e.g. Spain). A combination with states already covered by the unitary patent is not possible.
Since January 1, 2023, during the transitional period until the unitary patent system enters into force, the request for unitary effect can be filed for all patent applications intended for grant at the EPO, i.e. also for patent applications filed before the effective date. EP patents granted before June 1, 2023, cannot be "converted" into a unitary patent. However, deferment of grant until after June 1, 2023 can be requested in order to benefit from the unitary effect.