Why is the GST figure sometimes out by a factor of +/- $0.01?
Background: ContactsLaw offers the ability to enter a dollar figure against a product, which has the effect of adjusting the amounts billed for each member's time up/down on a pro-rata basis.
When an aggregate amount is distributed over several line items, as in the situation outlined above, rounding is performed; both in relation to the scaling factor (i.e. keeping the charge in proportion to the amount originally record), and in the application/removal of GST. This rounding is applied to both the ex-GST and GST component figures, the sum of which equals the inc-GST figure.
When the amounts lost or gained due to rounding are added up over several successive line items, the total difference may sometimes equate to +/- $0.01. If left unresolved, this would mean that the sum of all line items for the product would not equal the amount entered against the product by the user.
Rather than change the user's figure to the new total (after rounding), ContactsLaw will apply a correction to the GST component of the product. This will ensure that (depending on which figure the user provided) the ex-GST/inc-GST totals match the values provided.
Occasionally, this behaviour will result in a visually unappealing bill total. In this scenario, we recommend manually providing an inc-GST figure instead of an ex-GST figure (since the line items will always add to match the figure as provided).