What is an NMI and a MIRN on Australian energy bills

Every electricity connection in the National Electricity Market has a National Metering Identifier, almost always shortened to NMI. Gas connections have a Meter Installation Registration Number, or MIRN. They look like bureaucratic garnish on a bill. They are how the market knows which wires, which pipes, and which household it is talking about.

If you read an electricity bill only for the dollar figure, you will miss the one string that makes a switch, a move-in or a complaint attach to the right brick veneer.

The NMI is 10 or 11 digits, and it is not the meter number

A NMI is a unique 10 or 11 digit number assigned to the electricity connection point. It stays with the site when you switch retailers. The retailer brand on the bill changes. The NMI does not.

It is not:

• The account number, which is the retailer's own filing system.
• The meter serial number stamped on the metal or plastic case in the box.
• The street number, even if the street number is also 11 digits in a particularly unlucky suburb.

Meter serials identify a piece of hardware. NMIs identify the connection in the market standing data. Hardware gets swapped. The NMI should still point at the same site, with a new meter recorded against it. That is why a smart-meter appointment does not give you a "new NMI" as a souvenir, and why quoting the number on the glass to a comparison site often returns nothing useful.

Some older paperwork shows an 11-character NMI with a checksum. If a form asks for 10 digits and your bill shows 11, use the number exactly as the retailer printed it, or ask them which format the transfer system wants. Do not drop a digit because a web form looks tidy.

Where to find it

Look here, in order:

• The electricity bill, near the supply address, meter details or "your NMI" heading. This is the reliable copy.
• The retailer's app or online account, which is pulling the same record.
• Occasionally a sticker in the meter box. Treat that as a hint. Confirm it against a bill before you sign a contract.
• A previous tenant's bill, if you are moving house and they are willing to share the identifier, not their unused concession.

If you cannot find it, call the current retailer and ask them to read the NMI against the supply address. That is a normal request. Guessing from a neighbour's bill, or from a photo of someone else's meter in a Facebook group, is how wrong-site transfers start.

For a vacant property, the incoming retailer can often find the NMI from the address. Still ask them to read the address back, including unit numbers. "11/4" and "4/11" are different connections and have been the plot of more than one ombudsman complaint.

MIRN is the gas version

Natural gas does not use a NMI. It uses a MIRN — Meter Installation Registration Number — issued for the gas delivery point. You will find it on the gas bill. Some dual-fuel invoices list both identifiers in a dense block of type. Put the electricity number in electricity forms and the gas number in gas forms.

A MIRN matters when you compare gas plans, when you switch gas independently of electricity, and when a dual-fuel salesperson claims one signature moves both fuels. It does not. See dual fuel versus separate accounts. Electricity transfers ride on the NMI. Gas transfers ride on the MIRN. You can change one retailer and keep the other.

Some gas paperwork also mentions a DPI (delivery point identifier). If a retailer asks for a MIRN and you only have a DPI, ask them to translate. Do not invent digits.

Bottled LPG is a different product again. It will not have a MIRN of the network-gas sort. Do not hunt for one on a barbecue bottle.

Why comparison sites ask

A postcode tells a site which city you are in. A NMI tells it, through market standing data:

• Which distribution network you are on.
• Whether the meter is basic, interval or smart.
• Whether there is solar, and sometimes how it is configured.
• Whether a controlled-load register exists.
• The network tariff class the site sits on.

That is why Energy Made Easy and Victorian Energy Compare are more accurate when you identify the site properly. It is also why a telemarketer who already "has your NMI" may have bought a lead list, inherited it from a previous quote, or read it off a bill you held up at the door.

You can compare without a NMI, using usage from a bill. You will do more typing, and you may mis-specify the tariff. For a straightforward house it is workable. For a site with solar, controlled load or a demand tariff, the NMI saves you from comparing the wrong product.

Privacy: an identifier, not a secret handshake

A NMI is not a password. It appears on every bill a housemate might leave on the bench. Combined with interval consumption, though, it is a key to a household's pattern of life.

Sensible practice:

• Give it to a licensed retailer when you are actually signing up or querying a site.
• Give it to Energy Made Easy or Victorian Energy Compare, which are government tools.
• Pause before pasting it into a random "we beat any quote" form, a broker you have not researched, or a social-media DM.
• Ask how long a third party keeps it, and whether they on-sell marketing lists.

Retailers, distributors and metering providers have a job to do with standing data. That is not the same as a shopping site building a profile. If you are uncomfortable, compare with bill usage only, then supply the NMI later to the retailer you chose.

Do not publish a bill on a forum with the NMI visible if you can crop it. The risk is less "a hacker steals your electrons" and more "someone raises a transfer or a credit listing against the site".

Wrong NMI transfers

Transfers in the market systems attach to the NMI, not to the name on the doorbell. If the number belongs to the other half of a duplex, the other shop in a mall, or the house two doors down with a similar street number, the wrong account moves.

Warning signs:

• The welcome pack address is not yours.
• Neighbours mention a retailer change they did not request.
• Your old retailer says you have already left, while the lights are still on and nobody asked you.
• A new bill arrives for a unit number you do not occupy.

Call the incoming retailer immediately. Ask them to reverse or correct the transfer. Keep paying undisputed usage so you are not framed as a vacant site. If the retailer cannot unpick it, use the complaint process, then:

• EWON in New South Wales
• EWOV in Victoria
• EWOQ in Queensland
• EWOSA in South Australia
• Energy Ombudsman Tasmania
• ACAT in the Australian Capital Territory

Western Australia's identifiers exist too, but most south-west households are not choosing among east-coast retailers. Do not let a national comparison form talk you into a transfer that the WA market does not offer.

A short habit that prevents most of the drama

When you next pick up a bill, highlight the NMI and, if you have gas, the MIRN. Check they match the address. When a website or a salesperson asks for "the number on the meter", ask whether they mean the NMI or the serial. If they do not know the difference, they are not ready to move your account.

Those two identifiers are dull until they are wrong. Then they are the whole story.