Invoicing - GST Rounding

Note: the price/rates used below are outdated, this thread is to demostrate how GST rounding is applied for ACC invoicing.

I've detailed below how calculations for duration based services work at ACC. 

Calculating the amount for duration based services which are GST inclusive can prove tricky as the amount is rounded twice.

The way calculations are done is that the value is rounded after multiplying by the amount of minutes, and rounded again after adding GST. 

Let’s take the following example. Acupuncturist hourly rate including GST is $66.72 and $58.02 excluding GST.

If we were to create a GST inclusive invoice for an acupuncture treatment with 45 minutes as the duration, the calculation would work as below.

58.02 / 60 = 0.967 (hourly rate excluding GST divided by 60 minutes)
0.967 * 45 = 43.515 (value per minute multiplied by number of minutes)
43.52 (amount after rounding)
43.52 * 1.15 = 50.048 (GST added to value)
50.05 (total amount after rounding)

An alternative approach for regulation allied health duration based services would be to use a table and pair values in 5 minute slots such as below.