Who Has the Burden of Proof in a Tax Dispute With the ATO?

Most businesses walk into an ATO dispute expecting a fair fight: both sides present their case, the tribunal decides who’s right.

That’s not how it works.

In almost every tax dispute with the ATO, you carry the burden of proof. The assessment is presumed correct. And unless you can prove it’s wrong, it stands.

That’s not a technicality. It’s the single most important factor shaping whether you should fight, settle, or walk away.

What “Burden of Proof” Actually Means in a Tax Dispute

Let’s start with what sounds like a simple question: who has to prove what when you’re challenging an ATO assessment?

The answer is you. Not them.

Under Australian tax law, once the ATO issues an assessment, that assessment is presumed to be correct. The Commissioner doesn’t have to prove the numbers are right. The Commissioner doesn’t have to justify every assumption. The assessment itself is treated as evidence of the tax you owe.

Your job is to prove it’s wrong.

This sits in legislation. Sections 14ZZK and 14ZZO of the Taxation Administration Act place the burden squarely on the taxpayer in both Administrative Appeals Tribunal reviews and Federal Court appeals. You must show two things: first, that the assessment is excessive or otherwise incorrect; second, what the correct assessment should have been.

That second part catches people out. It’s not enough to argue the ATO got it wrong. You need to prove what the right number is.

And the standard of proof is the balance of probabilities. That means you don’t need to convince a tribunal “beyond reasonable doubt” like in a criminal trial. But you do need to show that your version of events is more likely than not to be correct.

Think about what that means in practice. You walk into a hearing. The ATO tables the assessment. That’s their case. Now it’s on you to dismantle it, number by number, with documents, witnesses, and a coherent alternative explanation.

If you can’t do that, the assessment stands.

Why the ATO Doesn’t Have to Prove Its Case First

This feels wrong to most business owners. You’re thinking: “How can they just assume they’re right?”

Because the system is designed that way.

Tax administration in Australia relies on self-assessment. You lodge returns. The ATO processes them, often accepting what you’ve declared. But when the ATO forms a different view and issues an amended assessment, that assessment carries legal weight.

The Commissioner is not required to prove the underlying facts that led to the assessment. The assessment itself is admissible as evidence. It can be tendered in a tribunal or court without the ATO needing to call witnesses, produce audit files, or justify every line of reasoning.

You’re the one who has to produce the evidence.

Does that mean the ATO never has to prove anything? Not quite. In certain situations, particularly where fraud, evasion, or intentional disregard of the law is alleged, the Commissioner must adduce some evidence to support serious allegations. But even then, the ultimate burden of disproving the assessment rests with you.

The practical effect is this: if you don’t have strong records, the ATO’s numbers will often be accepted as the best available estimate, even if they’re rough, even if they’re based on assumptions.

Default assessments are a good example. The ATO sees unexplained deposits in your bank account. They assess those deposits as income. You know some of them were loan repayments or transfers between your own accounts. But if you can’t prove what each deposit represents with loan agreements, sale contracts, or internal records, the tribunal will likely accept the ATO’s characterisation.

Can you articulate, with supporting documents, what every major transaction in dispute actually was?

If you can, you’re ahead of most taxpayers. If you can’t, you’re in trouble.

What You Actually Have to Prove (and What You Don’t)

Let’s get specific. When the burden is on you, what does “prove the assessment is excessive” really mean?

It means two things. First, you must show that the ATO’s assessment overstates your tax liability. Second, you must prove what the correct amount should be.

That second requirement is critical. It’s not enough to poke holes in the ATO’s reasoning. You can’t just say “the ATO’s numbers are wrong” and leave it at that. You have to establish an alternative figure, supported by evidence, that the tribunal or court can substitute.

Think of it this way: if you’re disputing a large income assessment, you need to show not only that certain amounts aren’t income, but also what they are. Are they loan repayments? Sale of capital assets? Return of capital? Non-assessable receipts?

You need documents. Loan agreements. Sale contracts. Bank statements that trace the flow of funds. Correspondence that shows the nature of the transaction at the time.

Your recollection five years after the fact will not be enough.

The same principle applies to deductions. If the ATO disallows a deduction, it’s on you to prove the expense was genuinely incurred, for a deductible purpose, and properly substantiated. Invoices, payment records, business purpose explanations. All of it.

Does the ATO have to disprove your version of events? No. The ATO can simply point to the assessment and say: “The taxpayer has not discharged the burden of proving this is wrong.”

And here’s the part that frustrates people: even if the ATO’s own reasoning during the audit was flawed, even if they changed their position multiple times, that doesn’t automatically shift the burden back to them. The assessment is still presumed correct. You still have to prove your alternative.

One case that reinforced this recently is Commissioner of Taxation v Liang. The Full Federal Court made it clear: the taxpayer bears the burden of proof in tribunal and court proceedings, and that burden doesn’t shift even when the Commissioner appeals an AAT decision in the taxpayer’s favour. The legal onus remains on the taxpayer to prove both that the assessment is excessive and what the correct position should be.

What this means for you: arguing about fairness or the ATO’s process won’t win the case. Evidence will.

The Kind of Evidence That Actually Moves the Dial

So what does “good evidence” look like when the burden sits with you?

Start with contemporaneous records. Documents created at the time the transaction occurred, not reconstructed years later when the ATO comes knocking.

Bank statements. Contracts. Invoices. Emails discussing the deal. Board minutes. Loan agreements. Sale documents. Payroll records. Ledgers. Reconciliations.

Third-party documents carry particular weight because they’re harder to fabricate or manipulate. A contract signed by both parties. A bank statement from the financial institution. An invoice from a supplier. These are the building blocks of a credible case.

Contrast that with what doesn’t carry weight: your assertions. Your belief about what happened. A narrative constructed after the fact with no supporting paper trail.

Tribunals and courts assess evidence critically. They look for consistency, detail, and corroboration. If your story relies on memory and good intentions, but the documents tell a different story, the documents will win.

Let’s take a practical example. The ATO assesses you on large cash deposits. You say they were loan repayments from a family member. What do you need to prove that?

At a minimum: a loan agreement or acknowledgment of debt (ideally signed at the time the loan was made), bank records showing the original advance, repayment schedule or correspondence about repayments, evidence the repayments match the deposits in question.

If you have all of that, you’re in strong shape. If you have none of that, just a family member willing to say “yes, I lent them money”, you’re in weak shape. Oral evidence alone, without supporting documents, is fragile.

The same principle applies across the board. Disputing whether a payment is income or capital? You need documents showing what the payment represents. Claiming a deduction for business expenses? You need invoices, receipts, proof of payment, and evidence the expense relates to your business.

Can you reconstruct records if they’re missing or incomplete? Sometimes. You can request bank statements from your financial institution. You can ask suppliers for copies of invoices. You can piece together a timeline from emails and correspondence.

But the further you move from contemporaneous, original documents, the weaker your case becomes.

And here’s the hard truth: if you operated a cash-heavy business with poor record-keeping, and the ATO has issued a large assessment based on estimates, your ability to discharge the burden of proof may be practically insurmountable. At that point, your energy is better spent negotiating outcomes, penalty remissions, and payment arrangements than fighting a case you’re unlikely to win.

How confident are you that your records can withstand scrutiny from an independent tribunal?

If the answer is “not very”, that should shape your strategy from day one.

Different Disputes, Different Proof Challenges

Not all ATO disputes are the same. And the burden of proof plays out differently depending on what kind of assessment or determination you’re challenging.

Let’s walk through the main types.

Ordinary income and deduction disputes

These are the bread and butter of tax disputes. The ATO says a payment is assessable income. You say it’s not. Or the ATO disallows a deduction. You say it was incurred for a deductible purpose.

In these cases, the burden is straightforward. You must prove what the payment represents, or why the expense is deductible, using the kind of evidence we’ve just discussed. Contemporaneous records, third-party documents, clear narratives.

The standard is balance of probabilities. If your evidence is stronger than the ATO’s position, you win. If it’s not, you don’t.

Default assessments based on estimates

Default assessments are tougher. These arise when you haven’t lodged returns, or the ATO believes your returns are unreliable, and the Commissioner estimates your taxable income.

The ATO might base the estimate on industry benchmarks, bank deposits, asset acquisitions, lifestyle analysis, or other indirect indicators. The estimate doesn’t have to be precise. It just has to be reasonable in the circumstances.

Your burden is to prove that the estimate overstates your actual taxable income and to establish what the correct figure should be. That usually means reconstructing your income and expenses from whatever records you can gather.

If you can’t do that, the default assessment will stand, even if it feels excessive.

The recent Liang case is a good example. A taxpayer challenged default assessments based on unexplained bank deposits. The Full Federal Court confirmed that the taxpayer bore the burden of proving the deposits were not income and of proving what his actual taxable income was. The taxpayer’s evidence was found insufficient, and the assessments were upheld.

Penalties and fraud or evasion allegations

When the ATO imposes administrative penalties, or makes a determination that fraud or evasion occurred (which extends the time limit for amending assessments), the burden of proof can shift slightly, but not as much as you might hope.

For penalties, you generally need to show that your conduct was not reckless or intentional, or that you took reasonable care, depending on the penalty being imposed.

For fraud or evasion determinations under section 170 of the Income Tax Assessment Act 1936, many taxpayers assume the ATO must “prove fraud”. That’s not quite right. The Commissioner can make the determination, and the burden then falls on you to prove that fraud or evasion did not occur.

In practice, this means proving that your actions, records, and disclosures were honest and in accordance with your obligations. It’s a difficult burden to meet if the ATO has pointed to patterns of non-disclosure, missing records, or inconsistent explanations.

Part IVA anti-avoidance provisions

Part IVA is the general anti-avoidance regime. If the ATO applies Part IVA to cancel a tax benefit you obtained, you bear the burden of proving that the scheme did not have the purpose (or one of the purposes) of obtaining a tax benefit, or that the relevant factors do not support the ATO’s determination.

This is a notoriously difficult burden to discharge because Part IVA involves subjective assessments of purpose and objective factors. The Commissioner’s determination carries weight, and displacing it requires clear evidence about the commercial drivers, substance, and purpose of the arrangement.

Again, contemporaneous documents are critical. Board papers, advice, transaction documents, correspondence. If the ATO says you entered a transaction to avoid tax, and your documents show otherwise, you have a case. If your documents are silent, or worse, support the ATO’s view, you’re in deep trouble.

Pre-filled and third-party data mismatches

Modern ATO systems pull data from banks, employers, share registries, and payment platforms. Pre-filled information populates tax returns. When there’s a mismatch, the ATO may amend your assessment based on that third-party data.

You might know the data is wrong. A bank reported a figure incorrectly. An employer made a mistake. A platform double-counted a payment.

The burden is still on you to prove the data leads to an excessive assessment. That means getting corrected statements from the third party, reconciling your own records, and showing the tribunal what the correct position should be.

Pre-filled data looks authoritative. But mistakes happen. And the legal framework hasn’t changed: the taxpayer must prove the assessment is wrong.

Can you map out, for each major issue in your dispute, what you would need to prove and whether you have the evidence to do it?

That exercise will tell you more about your prospects than any legal argument.

How the Burden of Proof Should Shape Your Strategy

Understanding the burden of proof is not academic. It should drive every strategic decision you make in an ATO dispute.

Let’s start with the threshold question: should you fight or settle?

If your records are strong, your alternative position is clear, and you can prove it on the balance of probabilities, fighting makes sense. You have a realistic prospect of success. The burden of proof is a hurdle, but it’s one you can clear.

If your records are weak, incomplete, or non-existent, fighting is usually a waste of time and money. You’re not going to win a case where you can’t discharge the burden of proof. At that point, your focus should shift to negotiation: can you settle for a lower amount? Can you get penalty remissions? Can you structure a payment plan?

The burden of proof is the lens through which you assess that decision.

Ask yourself: can I prove, with documents, that the ATO’s assessment overstates my tax? Can I prove what the correct amount should be? Do I have witnesses who can support my version of events with credible, consistent testimony?

If the answer to any of those questions is no, you need to recalibrate.

And here’s where early case theory matters. Before you lodge an objection, before you escalate to the AAT, sit down with your lawyer and map out the evidence. What do you have? What’s missing? Can you get it? Will it be enough?

That process often reveals uncomfortable truths. You thought you had a strong case because “the ATO is clearly wrong”. But when you start listing the documents you can produce, the case doesn’t look so strong anymore.

Better to have that conversation early, when you can still pivot to settlement, than after you’ve spent hundreds of thousands of dollars on a case you were never going to win.

The burden of proof also shapes how you prepare for hearings. You’re not just arguing the law. You’re building an evidentiary case. That means organising documents, preparing witnesses, briefing experts, and constructing a narrative that a tribunal will find more persuasive than the ATO’s position.

It means anticipating the ATO’s attack on your evidence and shoring up the weak points.

It means being honest about gaps and explaining them credibly, rather than hoping they won’t be noticed.

And it means testing your case theory against the standard of proof. If you were sitting as the tribunal member, would you find your evidence convincing? Would it tip the balance in your favour?

If not, why are you running the case?

One more thing: the burden of proof should inform how you conduct yourself during an audit. Once the ATO starts asking questions, they’re building the foundation for an assessment. The records you provide, the explanations you give, the positions you take, all of that will be used later if the dispute escalates.

If you’re sloppy during an audit, if you fail to substantiate claims, if you provide inconsistent information, you’re making it harder to discharge the burden of proof later.

The time to think about evidence is not after the assessment is issued. It’s now.

Practical Steps to Strengthen Your Position Before You Challenge

So you’ve decided to fight. What now?

Your first job is to gather every piece of evidence that supports your position. Not just the documents you think are important. Every contract, invoice, email, bank statement, ledger, reconciliation, board minute, and internal memo that relates to the issues in dispute.

Start with your own records. Then move to third parties. Banks, suppliers, customers, advisers, accountants. Request copies of anything they hold that might be relevant.

If records are missing, can you reconstruct them? Sometimes you can. Bank statements go back years. Suppliers may have copies of invoices. Email archives can be searched. Payroll records can be retrieved.

But reconstruction has limits. And reconstructed evidence is always weaker than contemporaneous records.

Next, organise the evidence. Create a timeline. Map each transaction. Show how the documents fit together and support your version of events.

This isn’t just about presenting information. It’s about building a persuasive narrative that makes sense of the facts and meets the burden of proof.

Then test it. Sit down with your lawyer and play devil’s advocate. What are the weak points? Where will the ATO attack? Can you plug the gaps?

If you can’t, does that change the strategy? Should you narrow the issues? Should you settle some points and fight others?

You should also consider whether expert evidence will help. In complex disputes involving valuations, industry practices, accounting standards, or technical tax issues, an independent expert can provide critical support.

But experts are only useful if you have underlying facts to support their opinions. An expert can’t fix a lack of records.

Finally, be realistic about costs. Litigation is expensive. AAT reviews can run into hundreds of thousands of dollars in legal fees, expert fees, and disbursements. Federal Court appeals cost even more.

If the amount in dispute doesn’t justify those costs, or if your prospects of success are weak because you can’t discharge the burden of proof, settlement is often the smarter commercial decision.

Winning a legal argument is satisfying. But losing a case because you couldn’t prove your position is both expensive and demoralising.

What evidence do you actually have right now, in hand, that supports your position?

If the answer is “not much”, get moving. The burden of proof won’t wait for you to figure it out later.

When the Burden of Proof Means You Should Walk Away

Let’s talk about the cases you shouldn’t run.

You’re angry. The ATO’s assessment feels wrong. You know they’ve made assumptions that don’t reflect reality. You want your day in court.

But if you can’t discharge the burden of proof, you will lose. And losing costs money, time, and emotional energy that you could spend elsewhere.

Here are the warning signs:

You don’t have contemporaneous records. You’re relying on reconstruction, memory, and oral evidence. The ATO has pointed to patterns of non-compliance or missing documentation. Your alternative position is vague or based on “that’s not how it happened” without supporting detail.

If any of those apply, your prospects are poor.

In those circumstances, your focus should shift. Can you negotiate a lower assessment? Can you argue for penalty remissions based on reasonable care or voluntary disclosure? Can you structure a payment plan that lets you move forward without crippling the business?

Settlement isn’t defeat. It’s pragmatism.

And here’s something most advisers won’t say bluntly enough: some cases are not worth fighting, not because the law is against you, but because the evidence isn’t there.

You might have a strong legal argument. But if you can’t prove the facts that underpin that argument, the legal argument is worthless.

The burden of proof is unforgiving in that respect. It doesn’t care about fairness. It doesn’t care that you think the ATO is wrong. It cares whether you can prove it.

If you can’t, you’re wasting money on a case you were never going to win.

A good lawyer will tell you this early. A great lawyer will help you pivot to a strategy that actually works: limiting the damage, negotiating outcomes, and moving forward.

The right question is not “can we argue this?” The right question is “can we prove this?”

If the answer is no, walk away.

The Bottom Line: Evidence Is Everything

Litigation is complex, yes. But the pathway through an ATO dispute shouldn’t be.

The burden of proof sits with you. You must prove the assessment is excessive and what the correct amount should be. The standard is balance of probabilities. And the evidence that will meet that standard is contemporaneous, third-party, and detailed.

If you have that evidence, you have a case. If you don’t, you’re better off negotiating.

The most important strategic decision you’ll make in a tax dispute is not about legal arguments or tribunal procedures. It’s about whether you can discharge the burden of proof.

Everything else flows from that.

At Aptum Legal, we help clients make that assessment early. We review the evidence, test the case theory, and give you honest advice about whether you can meet the burden. And if you can, we help you build the strongest possible case. If you can’t, we help you negotiate the best outcome.

Because clarity is the most powerful tool you can take into any dispute.

Disclaimer: This article is for general information purposes only and does not constitute legal advice. The content reflects Australian law as at the date of publication. Every tax dispute is different, and the burden of proof may apply differently depending on the specific facts and legal issues involved. You should obtain professional advice tailored to your circumstances before making decisions about challenging an ATO assessment or pursuing litigation.