Can my energy retailer back-bill me? Limits and your rights (2026)

What a back-bill is

A back-bill (or catch-up bill) is a bill for energy you used earlier but were not charged for, or were charged too little for. It usually follows a run of estimated reads that were too low, a meter that was not being read or was set up wrongly, a tariff applied incorrectly, or a billing system error. It can apply to electricity or gas.

Being back-billed does not mean you have done anything wrong. In most cases the retailer or the meter caused the undercharge, and that is exactly why the rules limit how far back they can go.

How far back they can go

NSW, Queensland, South Australia, the ACT and Tasmania

Under the national rules, a retailer can generally only recover undercharged amounts from the nine months before the date of the back-bill, even if the undercharge went on for longer.

Victoria

Since 1 January 2021, four months. A retailer can only recover undercharged amounts from the four months before it notifies you.

The exception

The limit does not protect you if the undercharge was your fault, for example if you did not allow access to the meter, or used energy unlawfully. In those cases there is no limit on how far back the retailer can go.

Paying it

You can ask for as long to pay a back-bill as the period it covers: a bill for six months of undercharged usage can be paid over six months. Your retailer must give you that time if you ask, even if it does not offer it.

If the bill is more than you can manage even spread out, ask about a payment plan or the retailer’s hardship program. Retailers must have one, and while you are on it and paying as agreed, they cannot disconnect you. See help if you can’t afford your bill and energy hardship programs.

Check it before you pay

1. Ask the retailer, in writing, to explain the back-bill: what period it covers, why you were undercharged, and how they calculated the amount.
2. Check that it does not reach back further than the limit for your state, unless they say you caused the undercharge, and ask for evidence if they do.
3. Check the meter readings it is based on. Photograph your meter with the date visible. See how to read your meter.
4. Check the rates. The undercharged usage should be billed at the prices that applied at the time, not today’s prices.
5. If you disagree, ask for the disputed amount to be put on hold while it is investigated. If the retailer does not resolve it, go to your state energy ombudsman.

If you were overcharged instead

The rules work the other way too. If you were charged too much, the retailer must tell you and credit the amount to your account, or refund it. If you find an overcharge yourself, raise it in writing as soon as you spot it.

How to spot it early

Back-bills are almost always preceded by warning signs: a bill marked "estimated" that looked low, a gap between billing periods, or usage that dropped sharply for no reason. See estimated meter reads.

When you upload your bills to EnergySorted, we line them up period by period, in usage per day, so a run of suspiciously low bills stands out before the catch-up arrives. Read is my electricity bill wrong? for the full set of checks, or check a bill free.