Understanding the invoice

What should I see on my invoice?

Your natural gas invoice should include the following information:

  • The dates and means for customers to report their meter readings
  • Actual and estimated consumption (associated quantities)
  • The price of energy and the tariffs applicable to the sale and consumption of energy (unit and total price)
  • The consumption band
  • The conversion factor
  • The total and unbundled value of the grid access tariff
  • The invoicing period
  • The applicable fees and taxes, itemised
  • The conditions, deadlines and means of payment
  • The consequences of non-payment
  • The amount of the discount corresponding to the social tariff, where applicable

The invoice should also include information on:

  • Any other services provided
  • CO2 emissions corresponding to the energy consumed and invoiced
  • Contact details of the supplier
  • Contact details for reporting faults and emergencies

See also the video on how to read your electricity and gas invoice.

 The final amount to be paid by the customer is calculated as follows:


In the absence of actual consumption data, the invoice will be based on estimated consumption (in full or in part). To avoid or reduce estimated consumption invoicing, report your meter readings to your supplier (or grid operator, if this is the contact) on a monthly basis, on the dates shown on your invoices. Find out more about reading your meter.


What is the conversion factor for natural gas?

Meters measure the consumption of natural gas in m3, but the consumption is invoiced in kWh. Since it is necessary to convert these two units (m3 and kWh), the conversion is made using a formula that takes into account, on the one hand, the higher calorific value (detailed information provided by the transmission system operator) and, on the other hand, the correction for temperature and pressure, as these vary from installation to installation.

The conversion factor and the explanation of its calculation are included in the invoice.


When can invoicing be adjusted?

Adjustments can be made in the following situations:

  • Correction of previous estimated consumption, after meter reading
  • Correction of measurement, reading and invoicing errors
  • Malfunction of the meter
  • Irregular consumption and energy theft


How is the adjustment made?

If the adjustment is in favour of the consumer, the amount must be credited on the adjustment invoice itself.

If the adjustment is in favour of the supplier, the consumer can ask to pay the amount in instalments: the number of instalments should take into account the number of months to be adjusted.

If the consumer is not responsible for the need for adjustment, no late interest can be charged.


What is the natural gas excise duty (IEC)?

It is a sub-category of the Petroleum and Energy Products Tax (ISP). It was introduced in 2013 and is included on natural gas invoices. Find out the value of the IEC.


Do invoices lapse/expire?

Yes. The natural gas supplier’s right to receive payment for the service provided lapses within six months of supply.

If, for whatever reason, the consumer has paid less than the amount consumed, the supplier’s right to receive the difference expires six months after the first payment.

In order for the limitation periods and expiry to have their intended effect, the consumer must expressly invoke his/her right near the supplier (preferably in writing).

If the invoice has already been paid, later invoking does not entail reimbursement of the amounts already paid.

Monthly lump sum agreements may also prevent the right to payment of the difference from lapsing, with the amounts submitted as a billing adjustment at the end of the agreement remaining outstanding.