As I mentioned, it’s a VERY bastardised invoice. I have sent them an email about it, but I don’t expect anything to change. You are correct, it IS immaterial whether GST is applied or not, but what isn’t is that I am given nice rounded ex-GST prices on some lines (without a line-by-line GST calculation appearing on that line), AND other lines have GST calculated from a GST inclusive price.
So I either have to click “tax included” and manually add it myself, or leave it NOT “tax included” and calculate an ex-GST price myself from the GST included prices on those lines.
(Did I say this was one bastard of an invoice? To clarify, it’s a “document” which contains several “parts” and each part is detailed enough in itself, but the totality of the document doesn’t line up with either line-by-line or total. In diagnosis, it appears each section uses different methods! AFAICWO it’s an issue that in one part of their accounting system prices are simply quoted ex-GST, yet in another part that relates to each user, there are values that have GST already applied and it is back-calculated and then it is all compiled into one document. It really does suck as far as invoices go. A high school economics student could do better).
That and the fact GST doesn’t appear line-by-line it is IMPOSSIBLE to get this to line up. I’m currently looking at @Brucanna’s suggestion here which might work as a work around, and may even be better than the suggestion above.