GST rounding is a well-known accounting issue that arises when you work backwards from a GST inclusive price.

All usage charges are calculated to 5 decimal places in our billing system but only show 2 decimal places on the bill. This means that when we adjust the figure from its 5 decimal place total down to 2 decimal places an element of rounding needs to occur. A figure that has the 3rd decimal place between 5 -9 will be rounded up and between 1 - 4 will be rounded down.

In respect to your residential bill:

GST of 15% can result in amounts of fractions of a cent that get rounded to whole numbers on your details page. However, we must account for all these fractions of a cent when we calculate the total correct amount of GST on the front page of your bill. The difference is usually not more than +/- 1-7 cents.

Why is the GST rounding calculation displayed?

Because on the current residential bill, if you added up all the GST inclusive usage amounts on the details pages of your bill, it will not always exactly add up to the GST inclusive amount on the overall total. Whilst the total amount owing has always been correct, this has caused confusion for some of our customers so we now incorporate a calculation that shows the rounding amount.

How does GST rounding appear on my bill for services at home?

The GST rounding amount is shown as a calculation at the end of the last details page of your bill so you can clearly see how your total charges are calculated.
This message will only display if there is a difference between the GST amount on your details page and the front page of your bill.

Have I been correctly billed GST in the past?

Yes, the total amount on your bill has always been correct in respect to this issue and matches the advertised price you signed up to. GST rounding is a necessary accounting measure with GST.