Most investors assume borrowing capacity is about income. Earn more, borrow more. And for the first property, maybe the second, that's essentially how it works. Then a different number starts to matter. One most investors have never calculated. And it stops them cold.
Debt-to-income ratio (DTI) limits have always existed in lending policy. What's changed is APRA's February 2026 macro-prudential cap: lenders can no longer write more than 20% of new residential loans to borrowers at or above 6x DTI. That limit doesn't appear on any application form. It appears as a decline, usually when you're already under contract and the clock is running. This edition walks through what DTI is, where the wall sits for most serious investors, how to calculate your own position, and what your options are when you're near or past the threshold.
DTI is simple arithmetic.
Total debt ÷ Gross annual income = DTI ratio
Total debt means everything: your home loan (if applicable), every investment loan balance, car loans, personal loans, and credit card limits (not balances, limits). Gross income is before tax. If you're applying jointly, it's combined gross.
The distinction that trips investors up: DTI is not the same as serviceability. Serviceability tests whether you can afford the repayments at a stressed rate (currently 3% above your actual rate). DTI is a blunter measure. It's the raw ratio of what you owe to what you earn, regardless of cashflow position. A high-income borrower with strong cashflow can still hit a DTI wall. Both tests apply independently. You need to pass both.
Key insight: Serviceability tells the lender you can afford the repayments. DTI tells them whether you already carry too much debt. They're different questions.
The threshold is 6x gross income.
At $180k gross income, the DTI math looks like this:
- 5.5x limit → $990k maximum total debt
- 6.0x limit → $1.08m maximum total debt
The gap between your current total debt and those ceilings is your remaining borrowing room. Most investors building their third or fourth property are closer to those ceilings than they realise.
Key insight: The wall doesn't move because your deal looks good. The ratio is the ratio. Structure your portfolio around it, not in spite of it.
Run these four steps before you need to borrow, not after:
Total your debt. Every loan balance. Every credit card limit (not the balance, the limit). Include PPOR, investment loans, car loans, personal loans. Ask your broker what their lender includes, as student debt treatment varies.
Use gross household income. Before tax. Include salary, salary sacrifice, and confirmed bonuses (lenders typically include 50–80% of bonus income). Rental income is included but shaded: lenders apply a factor of 75–80% to account for vacancy and costs.
Calculate current DTI. Total debt ÷ gross income. Note whether you're including a rental income shading factor, because the lender will.
Model the acquisition. Add the proposed loan to your total debt. Divide again. That's your post-acquisition DTI. Compare it to the 5.5x–6.0x range at major banks.
The single number most investors don't know is where they currently sit on this scale. Calculate it now. It takes ten minutes and it tells you a lot about what's actually available to you.
Key insight: Your DTI position isn't static. It changes with every new loan and every principal repayment. The investor who knows their current ratio can plan. The one who doesn't is just hoping the application goes through.
Four options. Each has real trade-offs.
Option A: Wait and let income grow. If income increases and debt stays flat, DTI improves automatically. A $20k income increase opens $120k of additional debt headroom at 6x. Slow, but it costs nothing. Works better if an income event (promotion, review, bonus qualification) is already in the pipeline.
Option B: Reduce debt deliberately. Principal repayments chip away at the numerator. This is the compounding benefit most investors miss when they think about the IO vs P&I decision. It's not just about equity or interest saved. It's about DTI headroom for the next acquisition. Switching a $560k loan from IO to P&I starts moving the number slowly, then faster.
Option C: Non-bank lender. More flexible DTI policy, faster to say yes. Higher rate, often 0.5%–1.0% above a major bank. On a $480k loan, that's $2,400–$4,800 per year in additional interest. If the acquisition is strong and the timing matters, the premium might still be worth paying. Model it properly before deciding.
Option D: Sequence the acquisition. Don't force it. Calculate when your income growth and principal reductions will bring you inside the threshold, then target that window. Use the interim period to build the deposit properly, narrow down the right asset, and not rush a $500k+ decision because of an arbitrary timeline.
Key insight: The DTI wall isn't a rejection. It's a timing signal. The investors who treat it as one build better portfolios than those who scramble for a workaround.
Sam is 41. Two investment properties: Brisbane house ($820k value, $560k loan) and a regional duplex ($480k value, $310k loan). Total investment debt: $870k. His principal place of residence is owned outright. Gross income: $180k.
Current DTI: $870,000 ÷ $180,000 = 4.83x. Well inside the threshold.
He's been modelling a third acquisition: a two-bedroom apartment in Brisbane's inner north. Purchase price: $600k. At 80% LVR, the loan is $480k. He runs the numbers.
| Before | After acquisition | |
|---|---|---|
| Total debt | $870k | $1,350k |
| Gross income | $180k | $180k |
| DTI | 4.83x | 7.5x |
7.5x. Hard no from every major lender. The deal looks fine on cashflow. The LVR is fine. The DTI is not.
Sam works through the four options. The non-bank path is available, but at 0.75% above his current rate, that's $3,600/year in additional interest for the duration. The deal has to carry that cost and still make sense.
He models Option D instead. His income review in July 2026 has a realistic upside of $195k–$205k. The Brisbane property switched to P&I at rollover (per the decision in the last edition), which means the loan balance will drop by approximately $8k–$10k in year one, modest, but it moves. If income reaches $205k by mid-2026 and the loan balance comes down to $550k, his total debt post-acquisition would be $1,330k. DTI: $1,330k ÷ $205k = 6.49x. Still above major bank limits, but well within non-bank range, and closer to the threshold than before.
At $225k income with the same debt: $1,330k ÷ $225k = 5.91x. Inside most major bank limits.
Sam's call: wait 18–24 months. Use the time to build the deposit properly, let income grow, let the Brisbane P&I do its work, and be specific about which apartment, because the one he was looking at wasn't the only option in that market.
The wall didn't stop the acquisition. It moved it 18–24 months and made it better.
DTI limits catch investors who've been doing everything right. A high DTI isn't a sign you've been reckless. It's a consequence of having built something. The system doesn't differentiate. It just divides. What I keep coming back to is how much better these decisions are when they're made early. When you know your DTI position before you need to borrow, the wall becomes a planning input, not a surprise. You can sequence around it. You can model when the window opens. You can decide whether Option C is worth the rate premium rather than scrambling to find a lender who'll say yes. The investors who hit the wall and panic are the ones who never knew they were approaching it.
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See you next week.
Alex
Next week: The Serviceability Buffer. What the 3% stress test actually costs you in borrowing capacity, and why two borrowers with identical incomes can walk away with very different approval numbers.
This article is for educational purposes only. It does not constitute financial, legal, or tax advice. Everyone's circumstances are different. Please seek professional advice before acting on any of the strategies outlined above.
Editorial notes: