The first type is the basic Maintenance release certificates (MRC). It will be issued by each Part-145 organization involved in line or base maintenance after verifying that the maintenance performed was completed correctly. This certification does not state that the aircraft is ready for service; it allows for certification of maintenance where maintenance has been carried out leaving the aircraft in a non-approved configuration.
This is important because certain tasks that are not treated as maintenance in the United States are treated as maintenance under the European rules (e.g. an engine removal that is not followed by any replacement).

The second type of certificate will be the base maintenance release certificate (BMRC). This is issued after all applicable MRCs have been issued, and after all maintenance tasks ordered by the operator have been completed (or properly deferred). It indicates that the work was completed correctly and that there are no known non-compliances that would represent serious hazards to flight safety. This certification does not imply that the aircraft is ready for service, because some additional line maintenance tasks may be required before flight.

The final type of release tag would be the certificate of release to service (CRS). This certificate would be issued before flight, after all the required MRCs and BMRCs, as applicable, have been issued. The issuance of the CRS implies that the aircraft is considered ready for release to service with respect to the work that has been ordered by the operator. As in the United States, the organization issuing the CRS is not responsible for work that has not been ordered by the operator and which may be mandatory (such as an AD) – that responsibility remains with the operator; however the CRS-issuer is responsible for all work ordered by the operator, (even if that work was beyond the abilities of the Part 145 organization)!