Invoice Tax Amount Rounding

Here is a summary of how Greentree calculates GST/VAT on invoices, and why you may sometimes see small rounding differences. 

Greentree like many other vendors uses line‑by‑line tax calculation instead of calculating tax on the invoice total. In most modern accounting and tax setups, line‑by‑line tax calculation is recommended over invoice‑total tax calculation.

Why line‑by‑line is preferred:

• Each line is treated as a separate taxable supply, which better matches how GST/VAT rules work (tax is applied per item/rate, not just on the final invoice total).
• It correctly handles mixed tax rates, exempt items, and discounts applied at line level on the same invoice.
• It keeps your general ledger postings accurate per line, because each line’s net and tax are posted to the correct nominal account.
• It reduces reconciliation issues when comparing Greentree to POS or other systems that also calculate tax at line level.

Because tax is calculated and rounded on each line and then summed, the final tax total can differ slightly from what you’d get if you applied the tax rate once to the invoice total and rounded. This behaviour is expected with line‑by‑line tax calculation.