How to Refinance and Quarantine Deductible vs Non‑Deductible Debt Now

The 2026–27 Federal Budget rewrites how property and investment returns are taxed, especially negative gearing and capital gains from 1 July 2027. To protect what deductions you still have, you need your loans cleanly separated so deductible and non-deductible debt are “quarantined” from each other and easy to trace. That usually means refinancing into clearly labelled splits and tightening how you use offsets and redraw.

In plain English: you want investment and business loans in their own splits, and home or personal debt in separate splits, with no mixing of purposes. If you act in the next 6–18 months, you can often fix messy structures without fire sales or panic moves.

This guide walks you through how quarantining works, why it matters more after the Budget, and the exact steps to refinance or restructure this week.

Separate loan splits by purpose make tax outcomes easier to manage under new rules.

1. Why quarantining debt matters more after the Budget

1.1 The new landscape: more tax, more scrutiny

The 2026–27 Federal Budget and the Treasury Laws Amendment (Tax Reform No. 1) Bill 2026 introduce:

1. Negative gearing reforms – rental losses on many established properties bought after 12 May 2026 will be quarantined from salary and other income from 1 July 2027.
2. Capital gains changes – the familiar 50% CGT discount is being replaced with CPI indexation and a 30% minimum tax on many capital gains for individuals.
3. Higher record-keeping expectations – Treasury and the ATO are explicit: if you claim deductions, you must show clear evidence of how borrowings were used.

As discussed in the Budget commentary and our broader guide on restructuring existing loans, middle‑Australia investors are in the firing line. The ATO will lean harder on loan purpose and tracing when checking what is deductible.

1.2 Purpose, not property, drives deductibility

Under long‑standing ATO principles (unchanged by the Budget):

• Interest is deductible if the borrowed money is used to earn assessable income (e.g. rent, business income, dividends).
• Interest is not deductible if it funds private purposes (home, holidays, school fees, cars).
• The property used as security is largely irrelevant – the key is what the borrowed money paid for.

This is the core rule behind debt quarantining. The reforms increase the value of every dollar of deduction you keep, and increase the cost of every dollar you lose because your structure is too messy to substantiate.

1.3 Quarantining in practice: what it actually means

“Quarantining” or “segregating” debt means:

• Separate loan accounts / splits for each major purpose:
  • Home (non-deductible)
  • Investment property purchases and costs (deductible)
  • Business or self-employed purposes (deductible, but separate from property)
  • Renovations or mixed-use assets where you may need to apportion.
• No mixing of withdrawals from those accounts – you don’t redraw from an investment split to pay for a holiday.
• Clear, written records (bank statements, settlement statements, spreadsheets) tracing where each drawn dollar went.

If you do this well, you can respond to the new rules – or a future ATO query – without panic.

2. How ATO tracing works – and how refinancing can break it

2.1 The ATO’s tracing approach in one page

The ATO looks at:

1. Original purpose – what did you actually use the borrowed funds for?
2. Subsequent redraws/repayments – if you redraw or top up, what were those extra funds used for?
3. Refinances and restructures – if you refinance, they trace through to the new loan.

Where a loan is used for mixed purposes (say 60% investment, 40% private), interest is usually apportioned. Over time, if you pay down the private portion faster, the deductible percentage can increase – but only if you can show the numbers.

2.2 Why sloppy refinances destroy clean deductions

Common traps that muddy the tracing:

• Rolling everything into one big 30‑year loan at refinance.
• Payout of personal loans and credit cards from an investment split.
• Using investment redraw for private spending, then trying to claim 100% of the interest.
• Reborrowing for a new property without creating a new split.

Once purposes are mixed inside a single undifferentiated account, your accountant may have to assume a conservative apportionment. In a post‑Budget world, that could mean losing thousands in deductions every year.

For a better way to consolidate without wrecking the tax story, see our guide on using home equity to consolidate debts sensibly: /insights/step-by-step-consolidate-debts-using-home-equity-no-restart.

2.3 Worked example: mixed loan, messy outcome

• Original $800k loan secured by your home:
  • $500k used to buy the home (non-deductible).
  • $300k equity top-up later used as the deposit on an investment unit (deductible).
• Years later you owe $700k.

If you never split the loan, that $700k is a blend of home and investment debt. Without detailed repayment tracking, your accountant might conclude, for example, that only 35–45% of interest is clearly linked to the investment.

If you had set up two splits from day one – $500k home and $300k investment – the interest on the $300k (subject to the new negative gearing rules) would be clearly deductible, and you could direct extra payments mostly to the home split.

Refinancing is your chance to fix this – but only if you restructure into the right splits.

3. What does “quarantining” debt look like in real life?

3.1 The clean, future‑proof structure

A simple, robust structure for a typical investor couple might be:

• Loan A – Home loan

  • Purpose: buy/renovate main residence.
  • Deductibility: almost always non-deductible.
  • Features: big offset account for buffers.

• Loan B – Investment loan 1

  • Purpose: purchase of first investment property.
  • Deductibility: interest generally deductible (subject to negative gearing rules) while property is rented.

• Loan C – Investment loan 2

  • Purpose: deposit and costs for second investment.
  • Deductibility: tied to second investment.

• Loan D – Business / self-employed split

  • Purpose: business working capital or equipment.
  • Deductibility: generally deductible against business income.

Each loan has its own statement, rate and repayment, and you never use an investment or business split for private costs.

3.2 Comparison: quarantined vs blended structure

For more on flexible structures, see /insights/designing-flexible-investment-loan-structures-geared-investors.

3.3 Offsets vs redraw when quarantining

Offsets and redraw both reduce interest, but they behave very differently for tax:

• Offset account – your cash is separate from the loan. Drawing money from offset does not change loan purpose.
• Redraw facility – funds you redraw become new borrowings from the ATO’s perspective. Purpose is determined by how you use the redraw.

For quarantining:

• Use offsets linked to home and investment splits to hold cash.
• Use redraw cautiously, only for the same purpose as the original borrowing.

4. Negative gearing changes and quarantining: how they meet

4.1 Old vs new negative gearing rules

Under current rules (broadly):

• Net rental losses can often be offset against salary and other income in the same year.

Under the 2026–27 reforms (based on Budget and Bill commentary):

• For many established residential properties purchased after 12 May 2026, from 1 July 2027 rental losses will be quarantined – generally only offset against future rental income or capital gains, not salary.
• Existing properties and qualifying new builds are expected to keep more generous treatment, but details will be in later instruments.

This creates two big challenges:

1. Tracking which property is under which rule set (old vs new, established vs new build).
2. Linking loan interest to each property so you know what is deductible, and how it’s quarantined.

4.2 Why segregated debt matters more now

If you own or plan to own:

• Pre‑reform properties (grandfathered rules), and
• Post‑reform properties (new, restricted rules),

you need to be able to show:

• Which loan split funded which property.
• How much interest relates to each.

If everything sits in one pool, apportionment becomes a nightmare and you risk:

• Overstating deductions and facing an ATO adjustment, or
• Under‑claiming and paying more tax than required.

Our broader cluster article, Should You Restructure Investment Loans When Negative Gearing Benefits Shrink?, explores the timing question. This guide focuses on how to restructure so those benefits are traceable.

4.3 Example: one old, one new property

Assume:

• Property 1 – bought 2024, established house, existing negative gearing rules apply.
• Property 2 – bought 2027, established house, subject to new quarantine rules.

You refinance in 2027 and set up:

• Loan B: $400k relating to Property 1.
• Loan C: $350k relating to Property 2.

From 1 July 2027:

• Interest on Loan B may still feed into your broader tax return relatively flexibly (subject to new CGT rules etc.).
• Interest on Loan C’s loss position may be quarantined.

Actionable insight: if you don’t separate those loans, your accountant may have to treat the combined interest as partly quarantined, partly not – a messy, conservative outcome that likely costs you cash.

For more context on timing and whether to refinance at all, see /insights/when-investors-should-refinance-or-sit-tight.