Gemini e-learning

Discover how to use every aspect of Gemini – and get the best from the system.

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    Learn how to use Gemini 

    We have a range of online training materials for customers to explore. They help you learn how to use – and get the most from – Gemini and Gemini Exit.  


    Get to grips with the Gemini user interface. 

    Gemini user interface familiarisation training


    Discover the different types of Gemini invoicing and file formats. 

    Gemini invoicing documents


    Understand the different reasons Nominations can become locked. 

    Nomination lock guide – shippers


    Understand the EU Nomination process. 

    EU Nomination guide – Shippers


    Learn how to use Gemini Exit confidently and efficiently. 

    Gemini Exit (NTS external) user guidelines – all chapters

    Gemini Exit (NTS external) user guidelines – individual chapters:

    1. Reports
    2. Introduction to processes
    3. Set up user preferences
    4. Capturing your requests
    5. Transfers and assignments
    6. OCS/OPS process
    7. Constraints


    Test your Gemini API set-up 

    Many of our customers use application programming interfaces (APIs) within Gemini. These are useful mechanisms for sending and retrieving large sets of data. 

    Useful API documentation

    The Gemini API User Guide has been written to give Gemini Users an overview of the API facility available in relation to the Gemini System.  Along with the Gemini Exit API Specification Document, which contains technical details on the structure of the APIs.

    Risk-free testing 

    Prior to any live set-up, you may wish to test your processes.

    To help you do that, we offer a secure, offline testing environment. It’s a mirror-image of the live Gemini API landscape and allows for true-to-life testing.  

    If you’d like to use the Gemini test environment, but aren’t registered, ask your Local Security Officer (LSO) to contact our Service Desk. 


    Call: 0845 600 0506 

    What information will the Service Desk need? 

    Our team will need to know: 

    • your Shipper organisation name and short code 
    • your start date and end date for access 
    • whether access is required to test APIs, online screens or both 
    • details of live Gemini User IDs to copy in the testing environment 

    For API testing, please give details of which APIs or API controllers will be tested. 

    For accessing and testing of screens, please confirm: 

    • which screens will be accessed 
    • whether data will be entered – and which fields will be used 
    • details of the test cases to be executed 

    Common queries

    To remove this lock, please call National Gas Transmission on 0370 191 0636. If you need further support, please call our Service Desk on 0845 600 0506. In both cases, you’ll be required to provide your Service ID, your User ID and the Gas Day.

    Your User ID could have been locked for one of the following reasons:

    • For GB Nominations, if two or more different User IDs try to update the same set of records (e.g. a combination of Service ID and activity number for that Gas Day), an error message will be displayed indicating that the records have been locked by another user.
      GB Nomination locks are auto-released after 60 minutes of the locks being applied. The user will get the same error message on the screen. Wait for 60 minutes for the locks to be auto-released.

    • For EU Nominations, if the same connection point and shipper combination are being used by two or more different users to update the EU Nomination for a Gas Day, the data will be locked.

    • The same restriction will occur if you select 'All' as the connection point and nominate using multiple User IDs. However, in this instance, all the connection points will be locked.

    Whenever you exit from the Update Nomination Screen, it's essential to click on the Cancel/Save button and exit. If you click on the red X in the top right- hand corner, the data will remain locked by that User ID.

    However, if the screen is left open, the lock will be in place for as long as the screen is open.

    First check that the system is not within the Gemini maintenance window.

    Maintenance windows

    Monday to Saturday 3:15am–4:15am

    Sunday 3am–5am

    If you’re trying to access the Gemini System outside of the Gemini maintenance window and are unsuccessful, you’ll need to raise a technical support request.

    If the Demand Attribution figure looks incorrect, you’ll need to call our Service Desk on 0845 600 0506.

    For any issues relating to Demand Attribution, you can raise a technical support request.

    You can request measurement data using the MEI file type. When the Gemini system has received the file, it will get processed and a response will be sent back via an MEO file type.

    The file formats are available via the UK Link System.

    (Then folder 01. SharePoint Archive/Gemini folder/Gemini File Formats folder/Energy Balancing Bulk Uploads and Downloads folder/choose 'Bulk Download of Pre-Closeout Measurement' document)

    *Access to secure links are only available to gas shippers and transporters. To gain access find out about accessing secure documents.

    There are 22 meter types in Gemini:

    Meter Type

    Meter Type Description


    Daily Metered Aggregate Interrupt


    Non-Daily Metered Aggregate


    National Balancing Performance Testing


    National Transmission System Linepack Off-take (OF)




    Onshore Field


    Local Distribution Zone Stock Change


    Entry Meter – Storage


    Shrinkage Account Meter


    Reject Gas/Flash


    Sub Terminal


    Exit Meter – Storage


    Exit Firm – Storage


    Exit Interrupt – Storage


    Unique Site


    Information Provisioning Input Balancing Meter


    Information Provisioning Output Balancing Meter


    Daily Metered Aggregate Firm


    Daily Metered Consumer


    Unidentified Gas


    Boil Off


    National Transmission System Boil Off

    Access secure links

    Some e-learning materials are secure and only available to Shippers and Transporters. 

    Get access