GST and tax

How GST is applied per line, tax-inclusive pricing and rounding behaviour.

GST is applied at 10% for GST-registered companies. A company that is not registered charges no GST at all — the effective rate is zero, not a hidden 10%.

Discounts reduce the taxable base

An invoice-level discount reduces the consideration, so it reduces what GST is charged on. The discount is pro-rated across the lines, and GST is charged on the discounted net.

This matters for BAS. Charging GST on the full line total and subtracting the discount afterwards over-declares GST and produces a document that does not add up. Every invoice satisfies:

subtotal − discount + tax = total

Invoicing — invoice totals
Subtotal$100.00
GST (10%)$9.00
Discount (10%)-$10.00
Total (AUD)$99.00
The totals panel as the invoice screen renders it, in the suite's row order: Subtotal, GST, Discount, then Total (AUD) in the gradient the app uses. The figures are the $100 / 10% case the source file itself uses — GST is charged on the discounted $90, giving $9.00 and a $99.00 total. Charging it on the full $100 would over-declare GST at BAS time and the document would not add up. The GST row is hidden entirely for a company that is not GST-registered. Source: src/lib/invoice-totals.ts, InvoicingModule.tsx, invoicing.module.css.
Worked example

A $100 ex-GST invoice with 10% off: the discount is $10, GST is charged on the discounted $90 and comes to $9.00, and the total is $99.00.

Turning GST registration off

Registration status is read when the invoice is built. Figures on screen match the saved invoice, so an invoice cannot show one set of numbers and store another.

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