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.

An eligible trading right holders 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 published on a quarterly basis in the following format. The MOS estimate publish date represents the latest date by which the MOS estimates should be published.

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.

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 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:

STTM MOS Estimates

MOS periods and MOS Offer Submission Dates

STTM Shippers must, for the purpose of rule 398(2)(b), 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. 

MOS Period Start Date

MOS Period End Date

MOS Offer Submission Date*

1 January

31 January

21 December

1 February

28 February**

21 January

1 March

31 March

18 February**

1 April

30 April

21 March

1 May

31 May

20 April

1 June

31 June

21 May

1 July

31 July

21 June

1 August

31 August

21 July

1 September

30 September

21 August

1 October

31 October

20 September

1 November

30 November

21 October

1 December

31 December

20 November

* All MOS offer submission are due by 17:00 hrs AEST on the date listed.
** In a leap year the MOS period ends on 29 February and the MOS offer submission date is 19 February 

MOS stacks

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


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