Smart IO and P&I splits to turbo‑charge tax and flexibility

Using IO and P&I splits well means putting non‑deductible home debt on principal & interest (P&I) and keeping deductible investment debt on interest‑only (IO), with clean, separate loan splits. Done right, you cut bad debt faster, maximise tax deductions and keep cashflow flexible enough to survive rate rises.

Here’s how that structure actually works in practice, and what to ask your broker and accountant to do this week.

Separating home and investment loans into clear P&I and IO splits improves tax clarity and flexibility.

The core idea: different rules for home vs investment debt

For tax, the ATO cares what the money was used for, not which property secures the loan.

So your two priorities are:

1. Home (PPOR) debt – non‑deductible
   Usually best on P&I, with extra repayments and/or an offset.

2. Investment debt – potentially deductible
   Often best on IO, especially when you’re still paying off a home loan.

A simple split structure might look like:

• Split A – Home loan P&I: $700,000 (non‑deductible)
• Split B – Home equity for investment IO: $150,000 (deductible)
• Split C – Investment property loan IO: $550,000 (deductible)

All three can sit with the same lender, but each has a single, clear purpose to keep tax tracing simple and refinancing flexible.

Why mix IO and P&I instead of just picking one?

1. Tax and cashflow work differently

• P&I on home debt shrinks the balance each year. That cuts future interest and speeds up the day you’re debt‑free.
• IO on investment debt keeps repayments lower and the balance higher. That means higher interest, but it can be tax‑deductible if the loan purpose is investment.

Example (indicative only):

• $700k home loan at 6.0% over 25 years P&I → about $4,515/month
• $700k home loan at 6.0% IO → about $3,500/month

That ~$1,000/month gap is why some households chose IO on their homes pre‑rate hikes. But because home debt isn’t deductible, that’s usually the wrong debt to keep hanging around.

2. Flexibility when things go sideways

Roy Morgan data shows over 30% of borrowers are now ‘At Risk’ of mortgage stress. One of the most effective practical levers is controlling your minimum required repayments.

A mix of IO and P&I splits lets you:

• Keep mandatory repayments as low as possible on deductible investment debt.
• Direct every spare dollar into your non‑deductible home loan or its offset.
• Temporarily reduce pressure by switching an investment split back to IO (if the lender allows) instead of touching buffers.