A paid/unpaid checkbox can hide a balance
For the fictional A$1,100 invoice, settled payments of A$300 and A$400 plus an entered A$100 credit leave A$300. A pending A$300 payment dated after the review date is not counted. A refund would reduce the amount applied and increase the arithmetic remaining balance. All entries must come from records you can verify.
Rebuild the history without counting twice
Give every entry a stable, unique ID. Keep amounts positive and choose the kind to control its effect; do not use a negative payment to represent a refund. Enter the status appropriate to the review date. A credit changes the calculation but does not itself prove that a valid credit document or customer agreement exists.
Use the remainder as a review result
Compare the result with the issued invoice, receipts and bank evidence. Zero means only that the entered arithmetic balances; omitted payments or duplicated source records can still make it wrong. The checker cannot update the original invoice or recover missing history. Keep payment references together so your next follow-up is based on a checked balance.
Keep a review record
Run the check again whenever an input changes. Invalid or incomplete input clears the previous live result and disables download, so an old answer is not presented as current. Downloads contain the check table only; they are not a tax invoice, payment receipt or successful invoice export. They do not update drafts, history, login or payment status.
business.gov.au: invoice and payment records · Reference for the underlying recordkeeping or calculation concept; not an endorsement of this helper.