How to Shift Investment Loans from Interest‑Only to P&I Safely

Switching an investment loan from interest‑only (IO) to principal‑and‑interest (P&I) can easily lift repayments by 30–60%. Done without a plan, that jump can smash your household budget, drain business cashflow and force rushed decisions like selling at the wrong time.

This guide walks you through how IO to P&I switches work in Australia, how to model the impact on your numbers, and practical ways to restructure or stage changes so you keep control of cashflow.

1. What actually changes when you move from IO to P&I?

An interest‑only investment loan means you’re only paying the interest charged on the balance for a set period (often 5 years), then the loan automatically reverts to principal‑and‑interest for the remaining term.

When the switch happens:

1. Your required monthly repayment jumps because you’re now repaying the original balance over a shorter remaining term.
2. Your tax position shifts because the interest (and therefore deductible expense) usually falls over time as you pay down principal.
3. Your risk profile changes – you’re building equity faster, but with tighter cashflow.

A quick worked example

Assume:

• Investment loan: $800,000
• IO period: 5 years, then 25 years P&I
• Rate: 6.5% p.a. (variable, interest calculated monthly)
• During IO: repayments are interest only

During IO (years 1–5)

Monthly interest = $800,000 × 6.5% ÷ 12 ≈ $4,333.

After IO ends (years 6–30, P&I over 25 years)

Monthly P&I ≈ $5,406.

That’s a jump of about $1,070 per month or 25%+ – and if rates are higher or the remaining term is shorter, the jump can easily be 40–60%.

If you’ve used the property as part of a broader strategy – maybe to support your business or future upgrades – that extra $1,000+ per month has to come from somewhere. That’s why planning the switch is just as important as choosing the property in the first place.

Understanding how repayments change is the first step to a safe IO to P&I switch.

2. Why IO to P&I changes feel bigger for business owners

For employees with stable salaries, a repayment jump is mostly a household budgeting problem. For self‑employed clients and small business owners, it’s a three‑way squeeze:

• Household expenses and school fees don’t drop just because the bank wants more.
• Business cashflow may already be lumpy and seasonal.
• Lenders often assessed you with a 3% APRA buffer, but your real‑world buffers may be much thinner.

From earlier guides, we know:

• New geared property should be treated as a business‑like risk centre, and each property should stand on its own cashflow without relying on optimistic drawings from the business (/insights/small-business-owners-gearing-into-property-risks-protections).
• Borrowing safely starts with clear cashflow maps and buffers before you take on extra commitments (/insights/cashflow-buffers-risk-management-borrowing).

When an IO period ends, you’re effectively taking on a new commitment – a much higher repayment – whether or not you sign a new loan contract.

The 2026–27 tax reforms make this even sharper

Federal Budget 2026–27 will tighten how negative gearing works, especially for established properties purchased after 12 May 2026. Depending on timing and your portfolio, you may:

• Lose the ability to offset some rental losses against other income.
• Need better records to support which properties are grandfathered.
• See after‑tax cashflow worsen even if pre‑tax numbers look the same.

The upshot: you can’t assume tax refunds will keep bailing out a cashflow‑tight strategy. Any IO to P&I switch should be tested on both pre‑tax and after‑tax numbers, as we do in /insights/worked-examples-after-tax-cashflow-investment-loans-before-after-reforms.

3. Step‑by‑step: Model your IO to P&I switch properly

Before you touch your loans, you need a clear, decision‑grade model. This doesn’t need to be fancy – a robust spreadsheet or a good broker’s calculator is enough – but it does need to be honest.

3.1 Map the current and future repayments

For each investment loan:

1. Note the current balance and interest rate.
2. Confirm when the IO period ends and the remaining term after that date.
3. Ask your broker or lender to quote:
   • Current IO repayments.
   • Future P&I repayments over the remaining term at the current rate.
   • Sensitivity at +1% and +2% interest rates.

This gives you three key repayment numbers:

• Today (IO).
• Switch day (P&I at current rate).
• Stressed scenario (P&I at higher rates).

3.2 Build a simple pre‑tax cashflow

Per property, list for the next 12 months:

• Gross rent (with a small vacancy allowance, say 5%).
• Non‑finance expenses (rates, strata, insurances, maintenance, management).
• Loan repayments on IO.
• Loan repayments on P&I.

This mirrors the practical model described in our cashflow article: you want a property‑level P&L that shows pre‑tax cashflow before and after the switch.

3.3 Add a basic tax estimate

For decision‑making, you don’t need full tax software, just a realistic estimate:

• Work with your tax agent to estimate your marginal tax rate.
• Calculate annual interest cost under IO and P&I scenarios.
• Roughly model the tax deduction change as principal reduces.

Remember: only the interest is deductible, not the full P&I repayment. Principal is just returning capital.

This gives you:

• Pre‑tax cashflow under IO and P&I.
• After‑tax cashflow under IO and P&I.

You want to see, in dollar terms, how much worse (or better) your pocket is each month post‑switch.

Modelling property-level cashflow helps you see the real impact on your pocket.

4. How big is the hit? Typical repayment jumps compared

Below is an indicative comparison of monthly repayments for a 25‑year term P&I, versus an initial 5‑year IO followed by 20‑year P&I, all at 6.5% p.a.

Figures are illustrative only. They’re rounded and don’t account for rate changes or fees.

Two takeaways:

1. The longer IO runs, the shorter the remaining P&I term, and the steeper the jump.
2. If you had gone P&I from day one, your repayment would be lower than the post‑IO figure – that’s the cost of delaying principal.

If your portfolio has several IO loans expiring within a 2–3 year window, you can get hit with multiple 30–40% repayment jumps in quick succession.

5. Practical levers to manage the switch without wrecking cashflow

Once you’ve modelled the numbers, there are several tools you can use – often in combination – to soften the impact.

5.1 Use offsets and redraw strategically

If you’ve been building cash in an offset account, the switch to P&I doesn’t have to be painful:

• Every dollar in offset reduces the interest you pay and therefore your required cash repayment.
• You can sometimes keep the same actual cash outflow by allowing the principal component to rise slowly while interest falls.

If most of your surplus has gone to extra repayments in redraw, be careful:

• Redraw is legally part of the loan, not separate savings.
• Each redraw for non‑investment or business purposes can change the tax character of the loan and complicate deductibility over time.

Where possible, avoid using redraw to prop up business working capital or personal spending. That approach has already been flagged as risky in several of our guides.

5.2 Extend or re‑shape the loan term

If cashflow is tight, stretching the remaining term back out to 25 or 30 years can reduce the monthly repayment even on P&I.

Pros:

• Frees up monthly cashflow.
• May avoid forced sales.

Cons:

• Higher total interest cost over the life of the loan.
• You’re relying on future self‑discipline to pay extra or future capital gains to bail you out.

For small business owners, a longer term can buy breathing room to invest in the business where returns may be higher, as discussed in /insights/balancing-business-expansion-and-investment-property-purchases.

5.3 Stage the switch across properties

If you hold multiple properties:

• Avoid having all loans revert from IO to P&I in the same 6–12 month window.
• Refinance or renegotiate to stagger expiry dates.

For example:

• Property A: move to P&I now while incomes are strong.
• Property B: extend IO by 2–3 years while you stabilise or grow business revenue.

This reduces the chance of a single macro shock (rate rise, business downturn) coinciding with several sharp repayment jumps.

5.4 Consider partial P&I or multiple splits

Some lenders allow split loans where part is IO and part is P&I:

• Example: $800k loan split into $500k P&I and $300k IO.
• You start reducing risk and building equity on $500k, while containing the repayment jump by keeping $300k IO.

Benefits:

• You can align each split with different risk tolerances or investment horizons.
• Splits also help keep loan purpose clean if you’ve used some equity for business funding, as recommended in /insights/using-investment-property-equity-support-small-business.

5.5 Proactively restructure underperforming properties

If your modelling shows a property will be deeply cashflow negative on P&I, even after tax and at realistic rents, you have three broad options:

1. Refinance and reset the structure – possibly to a sharper rate, longer term, or interest‑only with a clear exit plan.
2. Renovate or reposition to improve rent and long‑term value (see /insights/financing-rose-bay-renovations-extensions-rebuilds for how to fund upgrades safely).
3. Sell and recycle capital into better‑performing assets or your business.

Which option is right depends on the property’s fundamentals, your stage of life, and your business or career plans.

Business owners need to balance investment loan changes with operating cashflow and buffers.

6. Special considerations for small business owners and SMSFs

6.1 Protecting your operating business

For business owners, every extra dollar of investment loan repayment comes out of either:

• Personal drawings from the business, or
• Cash that could have been kept in the business as a buffer or expansion capital.

From our earlier work, three rules matter here:

1. Treat each investment as a stand‑alone risk centre – don’t assume your business can always top up shortfalls.
2. Maintain separate buffers for business and personal/investment, not one mixed pot.
3. Avoid using long‑term property debt to fund short‑lived business assets or tax bills – it raises total interest cost and concentrates risk.

Before locking in P&I repayments, check that doing so won’t:

• Push you into underpaying BAS, PAYG or super.
• Force you to cut necessary business investment like staff or marketing.

If it might, revisit your loan terms, timing or even your property mix.

6.2 When your SMSF has a property loan

If your SMSF holds a geared property, a jump from IO to P&I is even more sensitive:

• Contributions caps limit how much extra cash you can tip in.
• Rent may not cover higher P&I repayments and SMSF expenses.
• You must keep enough liquidity to cover tax and minimum pension payments.

For SMSFs, it’s critical to build a 5‑year fund‑level cashflow map, stress‑testing rent, contributions and repayments, as covered in /insights/smsf-property-loan-cashflow-planning.

Often, the safer path is to:

• Move to P&I earlier while the fund is in accumulation phase and contributions are strong.
• Or refinance to reset the term and rate, if allowed, well before IO expiry.

7. One‑week action plan: prepare before repayments jump

You don’t need to solve everything this week. But you do want a clear view of your risks and options.

Day 1–2: Gather data

• List each investment loan: lender, balance, rate, IO/P&I status, expiry date, remaining term.
• Download the last 12 months’ rental statements and property expenses.
• Pull your latest business and personal cashflow summaries.

Day 3–4: Build your model

• With your broker, calculate current IO and future P&I repayments for each loan.
• Run +1% and +2% rate stress tests.
• Draft a simple pre‑tax and after‑tax cashflow per property.

Day 5: Identify pressure points

Highlight properties where:

• Post‑P&I cashflow (after tax) is more than $500 per month worse than now.
• Your household or business buffer would drop below 2–3 months of expenses within 12 months of the switch.

Day 6–7: Plan your moves

With your broker and accountant, decide where to:

• Restructure terms (extend, refinance, or split loans).
• Stagger IO expiries across years, not months.
• Direct extra cash into offsets now to soften future P&I.
• Review problem properties for renovate/hold/sell decisions.

Then set diary reminders 12, 6 and 3 months before each IO expiry so you’re never forced into last‑minute decisions.

8. When switching to P&I early can actually reduce risk

There’s a temptation to extend IO “as long as the bank will let us”. That can make sense if:

• You’re still in an early business growth phase and need maximum flexibility.
• You have a clear strategy for using the freed‑up cash to build buffers or high‑return assets.

But there are times when moving to P&I earlier is the lower‑risk call:

• The property is close to neutrally geared and rents are strong.
• Your income is stable and you’ve already built adequate buffers.
• You expect tighter lender policies or tax rules ahead (as with the 2026–27 changes), and want to derisk on your terms.

By switching to P&I earlier, you:

• Start reducing the loan while rates are still manageable.
• Give yourself more time to adjust if business or household income dips.

This is especially relevant where your business and investment strategy are intertwined – for example, rentvesting while running a growing practice, as discussed in /insights/rentvesting-for-business-owners-live-where-you-want-invest-where-it-works.

FAQs

1. Should I always extend my interest‑only period if the bank offers it?

Not necessarily. Extending IO can preserve cashflow in the short term, which may be useful if your business is still stabilising or you’re building buffers. But it also shortens the remaining P&I term, making future repayment jumps bigger and increasing total interest paid. The right answer depends on your cashflow model, risk tolerance and how you’ll use the freed‑up cash.

2. Is it better to sell a property than switch to P&I on a negative cashflow investment?

Sometimes. If a property remains significantly cashflow‑negative on P&I even after realistic rent rises and tax, it may drag on your household or business for years. In that case, selling and recycling capital into a stronger asset or your business could reduce stress and risk. The decision should weigh transaction costs, tax consequences and your broader wealth plan.

3. How far ahead should I plan for interest‑only expiry?

Ideally, start planning 12–24 months before IO ends, especially if you have multiple properties or complex income. That gives time to refinance if needed, build buffers in offset accounts, and consider renovations or restructures. Leaving it until the bank letter arrives 1–2 months out often forces rushed, sub‑optimal choices.

4. Will the 2026–27 negative gearing changes affect my IO to P&I decision?

They can. For newer established properties bought after the cut‑off, your ability to use rental losses against other income may be restricted. That means after‑tax cashflow could be weaker than in past decades, making big repayment jumps harder to absorb. Factor the new rules into your modelling and get personalised tax advice before locking in long IO terms.

5. Can I switch just one investment loan to P&I and keep the others IO?

Yes, that’s often a sensible way to stage your risk. Many investors move the strongest property, or the one they plan to hold longest, to P&I first, while keeping others IO to preserve cashflow. Splitting your loans this way can balance equity building and flexibility, especially when business income is variable.

Key takeaways

• Moving from IO to P&I typically increases repayments by 30–60%, especially if the IO period has been long.
• A simple but honest pre‑tax and after‑tax cashflow model per property is essential before you make any decisions.
• Business owners must protect operating cashflow and buffers, not quietly sacrifice them to higher loan repayments.
• Tools like offsets, term extensions, splits and staggered IO expiries can soften the impact when used deliberately.
• Some underperforming properties may need renovation, restructuring or sale rather than simply rolling into higher P&I repayments.

If you’d like help modelling your IO to P&I switch across home, investment and business loans, book a free 15‑minute strategy call at localknowledge.finance/consult. Your tax, your loan, one expert – a CPA, Tax Agent and Mortgage Broker in one conversation – so you can make a clean, numbers‑driven decision this week.

General advice only.