GST rounding differences on general payments

Contents

    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
    Date05/03/2026
    Paid toMetro Office Supplies
    GL account6-5010
    ReasonInv 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.

    If you believe there is a genuine discrepancy beyond a rounding difference, please contact our support team at support@lawsupport.com.au.

    Updated on 25 May 2026

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