Annual Quantity (AQ)

Learn about Annual Quantity (AQ) and why it’s important to the gas industry. Find out how you can help keep AQ data accurate.

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    What is AQ? 

    The Annual Quantity (AQ) of a gas meter point is an estimate of the amount of gas that it will use in a year under seasonal normal weather conditions. It’s an important data item in the gas industry.


    Why is AQ important?

    There are two versions of  AQ that are updated at different times. Each is used for tasks that are important to keeping the gas industry running smoothly.

    AQ version When it's updated What it's used for
    Rolling AQ Monthly – if we’ve received a new meter read
    • sharing out gas every day 
    • validating new meter readings 
    • assigning a site to an End User Category
    Formula Year AQ Every 1 April, using the Rolling AQ from the previous 1 December 
    • setting the SOQ for Class 3 and 4 sites
      (SOQ – Supply Offtake Quantity or Peak Day Consumption – determines transportation charge rates and the amount of system capacity that the site requires

    How inaccurate AQs affect the gas industry 

    For non-daily metered sites (Class 3 and 4) in particular, an inaccurate AQ can have significant implications.   

    • The site will be assigned too much or too little gas every day. This will affect the quantity of unidentified gas each day. 
    • The site may end up in an inappropriate End User Category. This means the profile of gas allocation during the year won’t be suitable.
    • For meter point reconciliation there could be big swings of energy on the amendment invoice.
    • The site may be paying the wrong rates of transportation costs. It may be assigned too much or too little system capacity.
    • Meter readings may be rejected because they fail tolerances. This could also prevent transfer of ownership.
    • In extreme cases, there may not be enough system capacity for all users on that part of the network on very cold days. This could result in some customers losing gas supply.


    Help us make sure AQ data is accurate

    If you're a Shipper, wherever possible submit a meter reading at least once a month. This should keep the AQ up to date. 

    Find out your site's AQ 

    You can find out the AQ for any site you own by: 

    What to do if there’s no new AQ 

    If you don’t get notified of a new AQ, first check your meter read rejection files. If your reading was rejected, review the rejection codes to understand why.   

    If the reading was accepted before the cut-off date for calculation, check the .NRL file. This includes individual T98 records for each site that failed to calculate.  

    You can find the AQ calculation failure codes in our Shipper Rejection Codes document in the UK Link document secure area. 

    Access to our UK Link document secure area 

    All UNC parties are entitled to access the UK Link document secure area, which is a secure internal network.   

    If you haven’t already done so, you can apply for access by visiting our Accessing secure documents webpage.


    How an AQ is calculated 

    We calculate AQs for non-daily metered sites and daily metered sites. 

    Non-daily metered sites (Classes 3 and 4) 

    AQ is based on the consumption between two meter readings. These should be between 9 and 36 months apart.   

    The calculation is adjusted for the impact of the actual weather experienced in that period. It’s then converted to a 12-month estimate.  

    If a meter reading is accepted by the 10th calendar day of the month, we’ll try to calculate a new AQ. If successful, the new AQ will go live on the first day of the following month.  

    Otherwise, the reading will be considered in the following month’s calculations. If successful, a new AQ will take effect on the first day of the second following month.  

    We only use meter readings that are in our central systems. 

    Daily Metered sites (Classes 1 and 2)  

    The AQ is the total consumption between two meter readings 365 days apart (without any weather correction). We use the latest actual read accepted by the 6th calendar day of the month. The new AQ will go live on the first day of the following month. 

    We notify Shippers of their new AQ five business days before it goes live, using an automated file sent via the IX network. The communication file is the .NRL file which is hosted in the UK Link document secure area. You can apply for access by visiting our  

    Accessing secure documents webpage.


    AQ Issues

    Information relating to AQ specific issues is now detailed on the Customer Issues Register. This register is updated periodically and contains all the latest information on issues reported to us, together with details of work we’re carrying out to resolve them.

    Common queries

    There are no changes to how the system derives and calculates an Annual Quantity (AQ) value.

    Opening and closing reads are required for change of Supplier events (but no change in Shipper). This will then trigger an AQ calculation.