Market operator service (MOS)

Market Operator Service (MOS)

For the purposes of rule 398(1) of the National Gas Rules (NGR), AEMO publishes a notice requesting MOS increase offers and MOS decrease offers from Short Term Trading Market (STTM) Shippers for each STTM pipeline, no later than 20 business days before the start of a MOS period, which is the first day of every month.

For the purposes of rule 398(2)(b), STTM Shippers must submit final MOS increase offers and MOS decrease offers to AEMO by 5:00 pm on the 11th gas day before the start of a MOS period. These offers must be submitted into the STTM webexchanger in accordance with the STTM participant webexchanger user guide.

An eligible trading right holder must comply with the requirements of rule 399 and rule 400 of the NGR in respect of its MOS increase offer or MOS decrease offer.

The STTM participant webexchanger user guide, STTM Participant Build Pack, STTM Participant Build Pack Business Validation Addendum explain how to make compliant MOS offers.

These documents can be found here.

MOS estimates

Monthly MOS estimates will be released quarterly in the following format.

Monthly MOS Estimates Released Quarterly

MOS Estimate Publish Dates

June, July, August Estimated early April
(40 business days before 1 June)
September, October, November Estimated early July
(40 business days before1 September)
December, January, February Estimated early October
(40 business days before 1 December)
March, April, May Estimated early January
(40 business days before 1 March)

MOS estimates can be found in the following section MOS Estimates Reports and Data.

MOS stacks

All MOS stacks for current and future MOS periods are published to the AEMO webpage in the following format.


Methodology for determining MOS estimates

This is the methodology for determining MOS estimates required under clause 5.2(f) of the STTM Procedures.

Methodology for determining MOS estimates v3.0

MOS periods

As required in rule 396 of the NGR, MOS periods are for a calendar month.

MOS estimate reports and data

The MOS estimates reports and data, required under rule 397(1) of the NGR, for each MOS period can be found via the following link:


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