Refinancing a Property Portfolio: Smart IO vs P&I Decisions

Refinancing multiple investment properties is not just about chasing a lower rate on each loan. It’s a portfolio‑level decision: which loans stay interest‑only (IO), which move to principal & interest (P&I), and in what order, so you protect cashflow while actually reducing risk.

In practice, that means three things:

1. Treat your loans like one balance sheet, not a pile of unrelated mortgages.
2. Decide where IO still earns its keep, and where P&I is now the safer choice.
3. Build a 3–5 year refinancing plan that staggers fixed expiries and diversifies lenders.

This guide gives you a decision‑grade framework you can use with your broker and accountant this week.

Start with a one-page view of your entire property portfolio before changing any loan.

1. Start With a Portfolio View, Not Loan‑by‑Loan Tinkering

Before you change a single repayment type, you need one clear snapshot of your whole position.

1.1 Build a one‑page portfolio summary

For 3–5 property portfolios, a simple one‑page summary with each property’s value, loan, LVR, rent and lender materially improves your decisions compared with looking at loans individually (see /insights/refinancing-3-5-property-portfolio-step-by-step-lvr-lmi-game-plan).

Include for each property:

• Current value (conservative estimate or latest valuation)
• Current loan balance(s) and limit(s)
• Lender and product type
• Repayment type: IO or P&I, variable or fixed, expiry dates
• Interest rate (indicative)
• Weekly rent and basic expenses (rates, insurance, body corporate)
• Loan‑to‑value ratio (LVR)

Then add across the bottom:

• Total portfolio value
• Total debt
• Overall LVR
• Total monthly repayments (P&I plus IO interest)
• Total monthly net rent after basic property costs

This is the dashboard you’ll use for every IO vs P&I call.

1.2 Stress test with a 3% rate buffer

APRA expects banks to use at least a 3% buffer above actual rates to test serviceability. As a portfolio investor, you should do the same for your own safety.

Use your one‑page summary to model:

• All variable and expiring fixed rates +3.0%
• Rents flat for two years
• Three months vacancy per property over a 12–18 month period

This is consistent with earlier guidance that portfolio refinancing decisions should be stress tested at least 3% above current interest rates with flat rents and three months vacancy per property to check resilience (see /insights/refinancing-3-5-property-portfolio-step-by-step-lvr-lmi-game-plan).

If the numbers only just work at today’s rates, locking in more P&I might feel “responsible” but could push you into distress if rates move again.

1.3 Worked example: the 4‑property investor

Assume:

• 4 properties, each worth $800,000 (total $3.2m)
• Total loans $2.24m (overall LVR 70%)
• Mixed IO and P&I, average rate 6.2% p.a.

Indicative current monthly repayments:

• If all IO at 6.2%: $2.24m × 6.2% ÷ 12 ≈ $11,573/month
• If all 30‑year P&I at 6.2%: ≈ $13,716/month

Difference ≈ $2,100/month.

Now apply a 3% stress:

• IO at 9.2%: ≈ $17,173/month
• P&I at 9.2%: ≈ $19,100/month (rough)

The gap remains around $2,000/month, but the absolute numbers are much bigger. That extra $2,000 could be the difference between coping and selling.

This is why the IO vs P&I choice is a portfolio cashflow call first, tax and “debt reduction” second.

2. IO vs P&I: What Changes When You Have Multiple Properties?

At one property, the IO vs P&I decision is mostly about cashflow and long‑term interest cost. In a portfolio, there are extra layers: tax, sequencing and lender policy.

2.1 The core trade‑offs

Interest‑only (IO) on investment loans usually:

• Maximises short‑term cashflow
• Keeps debt higher for longer, so total interest paid is larger
• Often keeps more of your income available to pay down non‑deductible home debt
• Leaves you more exposed if rates or vacancies move against you

Principal & interest (P&I) usually:

• Reduces debt and risk over time
• Increases monthly repayments now
• Creates “forced savings” via principal reduction
• Reduces future flexibility (you can’t redraw without changing tax tracing and purpose)

Post‑2027, tax changes mean you should assume minimal or no wage‑offset negative gearing benefit on established properties (see /insights/refinancing-investment-property-vs-home-whats-different). That pushes the decision even more towards pre‑tax cashflow and risk, not tax refunds.

2.2 IO and P&I across a portfolio: who should do what?

A practical rule of thumb for many investors:

1. Home loan first: Any non‑deductible owner‑occupier debt should almost always be P&I, and often aggressively so.
2. Core long‑term investments (high‑quality assets you expect to hold 10+ years): IO can still make sense if it materially improves cashflow and you’re disciplined about using the surplus.
3. Marginal or high‑LVR investments (thin yields, 90% LVR, or in weaker markets): P&I is often safer to slowly de‑risk.
4. Future sale candidates: IO with strong offsets can be fine, but only if you have a clear exit timetable and strong buffers.

This is the logic behind using IO and P&I splits across home and investment loans for better tax and flexibility, explored further in /insights/refinance-investment-loan-interest-only-to-principal-and-interest.

2.3 When IO still makes sense at portfolio level

IO can still earn its keep where:

• Rent barely covers interest and costs even on IO, but you’re in a clear “land‑bank” play (e.g. townhouse site, future zoning uplift)
• You have significant non‑deductible home debt and are using the IO surplus to hammer that balance down
• You’re in a high‑growth phase (e.g. growing from 2 to 6 properties) and carefully managing overall LVR to avoid extra LMI (/insights/grow-from-2-to-6-properties-without-extra-lmi-worked-scenarios)

But with multiple properties, you want intentional IO, not “everything IO because that’s what we’ve always done”.