GST rounding differences on general payments

If you have noticed a one-cent difference between the GST shown in Law App and the GST shown on a supplier’s tax invoice, this is almost always a rounding difference — and in most cases, Law App is correct.

Seeing it in action

Here is a real example. The supplier invoice below shows two line items and calculates GST as $32.12. Law App records the payment and shows GST as $32.13.

Supplier invoice

Metro Office Supplies

ABN 12 345 678 901 · Tax Invoice No. 1042

To: Sample Law Firm · Date: 14/03/2026

Description	Amount
Stationery supplies — March 2026	$301.27
Printer paper, 4 reams @ $5.00	$20.00
Subtotal	$321.27
10% GST Incorrect	$32.12
Total	$353.39

Law App — general payment

Law App — General Account Payment

Details · Documents · History

Payment details

Payment ref.	GP100001
Date	05/03/2026
Paid to	Metro Office Supplies
GL account	6-5010
Reason	Inv 1042 — March stationery
Net amount (ex GST)	$321.26
GST (calculated) Correct	$32.13
Gross amount (inc GST)	$353.39

Why the difference?

The subtotal on the invoice is $321.27. Ten percent of $321.27 is $32.127 — a fraction of a cent. That fraction must be rounded to the nearest cent.

Line 1 — stationery	$301.27
Line 2 — printer paper	$20.00
Subtotal	$321.27
× 10% GST (unrounded)	$32.127
Rounded correctly	$32.13 ✓
As shown on supplier invoice	~~$32.12~~

The ATO’s rounding rule is to round 0.5 cents upwards. $32.127 rounds to $32.13, not $32.12. The supplier has rounded down incorrectly. Law App is following ATO guidelines.

Does it matter?

For practical purposes, no. The ATO does not require cents when reporting GST on your BAS — amounts are rounded to whole dollars at lodgement. A one-cent difference has no impact on your compliance obligations.

Can I override the GST amount in Law App?

No. Law App does not allow the GST amount on a general payment to be manually adjusted. This is intentional — the system calculates GST correctly, and allowing manual overrides for cents-level differences would create inconsistencies without any compliance benefit.

What should I do?

You can process the payment as recorded in Law App. If you wish, you may raise the rounding difference with your supplier so they can review their invoicing process — but there is no obligation to do so, and no action is required on your end in Law App.

In short: Law App is following ATO guidelines. The supplier invoice contains a rounding error of one cent. This has no consequence for your GST reporting or BAS lodgement.