The Market Liquidity Obligation (MLO) is a market making requirement designed to facilitate transparency and liquidity in the trading of electricity futures contracts relating to a forecast reliability gap. The MLO commences when the Retailer Reliability Obligation (RRO) is triggered and provides a source of qualifying contracts for liable entities to purchase to help meet their RRO contracting requirements.
Initial MLO generators and MLO groups were determined in transitional rules made up until 30 June 2021 to implement the RRO. Subsequent MLO determinations and variations are made by the AER in accordance with the MLO Guidelines.
There is a requirement for market participants with scheduled generating units or scheduled bidirectional units to notify the AER of any updates or changes to their portfolio information to ensure the MLO register remains accurate – for more information please see the fact sheet below.
RRO generator portal
To facilitate the development of the MLO register, the National Electricity Rules required the AER to publish a MLO information template by 31 October 2020. To streamline the information gathering process, the AER launched an online RRO Generator Portal to streamline the provision of generator information. The generator portal replaced the MLO information template that was published in October 2020.
Market Generators in the NEM with portfolios that included scheduled generating units received an email including an invitation to join the RRO Generator Portal in late 2020.
The National Electricity Rules required all Market Generators with scheduled generating units to provide the information outlined in the portal by 31 January 2021.
If you believe you should have access to the portal, please contact the RRO team. The AER has also published a guide to assist market participants in using the online portal. Any questions about submitting information through the portal can be directed to the RRO team at RRO
aer [dot] gov [dot] au (RRO[at]aer[dot]gov[dot]au).
AER - RRO Generator Portal - User guide - December 2020
MLO register
The National Electricity Rules require the AER to establish, maintain and publish the MLO register in accordance with the MLO Guidelines. The MLO register replaces the deemed list of generators in the transitional rules, and outlines the MLO generators and MLO groups in participating NEM regions responsible for performing the obligation from 1 July 2021.
Market participants that have scheduled generating units or scheduled bidirectional units in their portfolios are reminded of the requirement to update the information in the RRO portal within 10 business days in the event the details of their scheduled generating or bidirectional units change. This is to ensure the MLO register remains accurate. This is necessary for all participants with scheduled generating units or scheduled bidirectional units, not only those existing MLO generators and MLO groups.
If you have any questions about the MLO register, please contact the RRO team at RROaer [dot] gov [dot] au (RRO[at]aer[dot]gov[dot]au).
The MLO register was updated in February 2025. The following change has occurred:
- Origin Energy has been designated as a MLO group for the South Australia 2026–27 reliability gap period, due to the extension of Osborne Power Station’s operation.
MLO Exchanges
There are two exchanges on which MLO groups and MLO generators and liable entities can trade MLO products: the ASX24 and the FEX.
The annual review process for the MLO exchanges is set out in the AER’s Interim MLO Guidelines and clause 4A.G.23(f) of the National Electricity Rules. The AER completed its annual review of the MLO exchanges for 2024 in December 2024 and concluded both MLO exchanges would maintain their registrations.