The implementation of the project is contractually regulated in the Grant Agreement. The European Commission has introduced a Model Grant Agreement that is used for all EU funding programs.

For multi-partner projects under Horizon Europe, the conclusion of a Consortium Agreement is generally mandatory. This agreement regulates the rights and obligations of the project partners among themselves. The content is not controlled by the EU Commission. It is not a contracting party. The provisions of the Grant Agreement remain unaffected by the provisions of the Consortium Agreement.

The preparation as well as the conclusion of the Grant Agreement is done online in the Funding & Tender Opportunities Portal. The legally binding signature is provided by the project-specific PLSIGN (the LSIGN assigned to the project and authorized to sign for the respective institution) in the portal. Before the Grant Agreement can be signed, the PLSIGNs of the individual consortium partners must also sign the "Declaration of Honour" (DoH) electronically in the Participant Portal.