Substantiation (proving a deduction)
The records that turn a claim into a defensible deduction.
Substantiation is your evidence that a deduction is real and work-related — receipts, invoices, bank statements, a logbook or a diary. The ATO’s position is simple: if you can’t show it, you can’t claim it. Records generally need to be kept for five years from lodgment.
Worked example
A $400 monitor bought for work needs the receipt and a sensible work-use share. Use it 80% for work and you claim $320 — with the record to back the 80% up.
Common mistake
Relying on a bank statement alone. It proves you spent money, not what you bought or why it was work-related — which is the part that actually gets tested.
Grounded in ATO guidance. Figures last checked . General information, not tax advice.
Related terms
Tax deduction vs tax offset
A deduction lowers income taxed; an offset lowers tax owed.
Logbook method (car expenses)
Claim your car’s real business-use share of running costs.
Tax invoice
The GST-compliant invoice that lets a buyer claim the GST back.
Depreciation (decline in value)
Claiming the cost of a big asset gradually over its life.
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