Under the Convention, all Parties should report on the steps they are taking to implement the Convention (Articles 4.1 and 12).
National communications (NCs) are submitted by Annex I Parties every 4–5 years following decisions for each submission by the Conference of the Parties (COP). They are prepared and reported periodically by Annex I Parties based on agreed reporting guidelines (decision 4/CP.5).

The COP, by decision 1/CP.16, decided that developed country Parties should enhance reporting in NCs and submit biennial reports (BRs), which outline progress in achieving emission reductions and the provision of financial, technology and capacity-building support to non-Annex I Parties, building on existing reporting and review guidelines, processes and experiences.
The COP also decided, among other things, that developed country Parties shall submit the first BR by 1 January 2014 and the second and subsequent BR two years after the due date of a full NC (i.e. 2016, 2020), and in the years when the full NCs are submitted, BRs can be presented either as an annex to the NC or as a separate report.

Decision 19/CP.18 adopted the biennial report common tabular format (BR CTF) that consists of 27 tables designed to facilitate the provision of information by developed country Parties.
To facilitate flexible search queries of the BR CTF data submitted by developed country Parties, the secretariat has launched the Biennial Reports Data Interface (BR-DI) application.

The secretariat prepares compilation and synthesis reports of the information provided in the NCs and BRs by developed Parties.

The report highlights findings on quantified economy-wide emission reduction targets; progress made towards their achievement, including information on mitigation actions and their effects; the estimates of emission reductions and removals and the use of units from market-based mechanisms and LULUCF activities; greenhouse gas (GHG) emission trends and projections; and the provision of financial, technological and capacity-building support to developing country Parties.