Cashflow Modelling for Geared Property: Real Numbers, Real Risks

Property gearing decisions go wrong when people buy a story, not the numbers. Cashflow modelling for geared property means building a simple, realistic profit and loss for an investment property – including tax – and then stress‑testing it before you sign a contract or refinance. Done properly, it tells you in dollars per month what the property will likely cost or produce in your real life.

This guide gives you a practical, spreadsheet‑ready framework with worked examples you can run this week – whether you’re a first‑time investor, a refinancing home owner, self‑employed, or running a small business on top of it all.

A geared property behaves like a small business: income, expenses, finance costs and tax.

1. What cashflow modelling for geared property actually means

Think of a geared investment property like a small business: income, expenses, finance costs, tax, and risk. Cashflow modelling is simply:

1. Estimating realistic rental income.
2. Listing every ongoing cost (including a sinking fund for future repairs).
3. Adding loan repayments at realistic interest rates.
4. Calculating your taxable profit or loss and likely tax impact.
5. Stress‑testing for rate rises, vacancies and income drops.

If you’re new to gearing, it’s worth first reading Plain-English Gearing Basics Every Australian Property Investor Must Know so you’re clear on negative vs positive gearing and upcoming 2026–27 tax changes.

Key definitions

• Geared property – you’ve borrowed to buy it.
• Negative gearing – rent < interest + expenses, so the property makes a taxable loss you may be able to offset against other income (subject to new rules for properties bought after May 2026).
• Positive gearing – rent > interest + expenses, so the property makes a taxable profit.
• Neutral/near‑neutral – around breakeven before or after tax.

APRA requires lenders to add around a 3% serviceability buffer above actual rates for new loans, so your modelling should do something similar.

2. The 7‑line cashflow model you can build today

You don’t need fancy software. A simple seven‑line model in a spreadsheet will do.

Step 1 – Property and loan assumptions

For each property, set up assumptions:

• Purchase price
• Loan‑to‑value ratio (LVR) and loan amount
• Interest rate (P&I vs interest‑only)
• Rent per week and expected vacancy
• Other operating costs
• Your marginal tax rate

We’ll use this base example:

• Purchase price: $750,000 (Sydney unit)
• LVR: 80% (20% deposit + costs from savings/equity)
• Loan: $600,000
• Rate (P&I, 30 years): 6.0% p.a. (indicative only)
• Weekly rent: $750
• Vacancy: 2 weeks per year
• Other annual costs: $12,000 (see breakdown below)
• Marginal tax rate: 37% + Medicare (assume 37% for simplicity)

Step 2 – Fill in the seven lines

1. Gross rent (per year)
$750 × 50 weeks (allowing 2 weeks vacancy) = $37,500

2. Non‑finance property expenses (per year)
Rough working example:

• Council + water: $2,800
• Strata: $4,500
• Landlord insurance: $1,000
• Property management (7.7% of rent): ~$2,900
• Repairs/maintenance allowance: $1,800

Total: $13,000

(You can tighten this with real quotes.)

3. Net rent before interest
= Gross rent − Non‑finance expenses
= $37,500 − $13,000 = $24,500

4. Interest expense
For a $600,000 loan at 6.0% interest‑only:
$600,000 × 6.0% = $36,000 per year

If you’re on P&I, the repayment includes principal, but only the interest is deductible. For cashflow, you care about the total repayment; for tax, you care about interest only.

30‑year P&I at 6.0% is roughly $3,600 per month, or $43,200 per year. At the start, about $36,000 of that is interest and $7,200 is principal.

5. Taxable result
Taxable profit/loss = Net rent before interest − Interest

• $24,500 − $36,000 = −$11,500 taxable loss (negative gearing)

6. Estimated tax impact
At a 37% marginal tax rate:
Tax saving ≈ $11,500 × 37% ≈ $4,255

7. After‑tax cashflow (P&I)
Cash cost before tax (P&I) = Non‑finance expenses + P&I repayments − Gross rent

• Expenses + repayments = $13,000 + $43,200 = $56,200
• Net before tax = $56,200 − $37,500 = −$18,700 (out of pocket)
• After‑tax cost ≈ −$18,700 + $4,255 = −$14,445 per year

That’s around $1,200 per month after tax leaving your pocket.

Under older rules, this loss might have been fully offsettable. Under 2026–27 reforms, new established properties may have losses quarantined, so the tax saving may be lower or deferred. Don’t build a strategy that only works with full negative gearing benefits.

3. Real‑world scenarios: negative, neutral and positive

Let’s expand this into three clear scenarios with numbers you can copy.

Seeing three gearing scenarios side‑by‑side highlights how loan size and rent shape cashflow.

Scenario A – Classic negative gearing (similar to many capital‑city units)

Assumptions:

• As above, but with modest rent growth and no major repairs

Year 1 after‑tax cost: ≈ $14,400 per year (~$1,200/month).

Now run a 5‑year view with modest changes:

• Rent grows 2% p.a.
• Expenses grow 3% p.a.
• Rate averages 6–6.5% (say, 6.25% overall)

You’ll likely find the property remains slightly negatively geared on a P&I loan unless rent jumps or rates fall.

If your household has spare cashflow of $2,000 per month, this may be manageable. If you’re self‑employed and income is lumpy, it could be tight.

Scenario B – Near‑neutral geared house in a regional centre

Assumptions:

• Purchase price: $600,000 (regional house)
• Loan: $480,000 (80% LVR, P&I at 6.0%)
• Weekly rent: $650, 2 weeks vacancy
• Non‑finance expenses: $10,000 p.a.

1. Gross rent: $650 × 50 = $32,500

2. Net before interest: $32,500 − $10,000 = $22,500

3. P&I repayment: $480,000 @ 6.0%, 30 years ≈ $2,875/month = $34,500/year
Interest component initially ≈ $28,800

4. Taxable result: $22,500 − $28,800 = −$6,300 loss
Tax saving @ 37% ≈ $2,331

5. Cash result (after tax):

• Cash outflows (repayments + expenses): $34,500 + $10,000 = $44,500
• Net before tax: $44,500 − $32,500 = −$12,000
• After tax: −$12,000 + $2,331 = −$9,669/year (~$805/month)

This is still negative, but far closer to neutral than Scenario A.

Scenario C – Positively geared older unit with low debt

Assumptions:

• Purchase price: $550,000 (older unit, bought years ago)
• Current loan: $250,000 (P&I at 6.0%)
• Weekly rent: $650, 2 weeks vacancy
• Non‑finance expenses: $11,000

1. Gross rent: $650 × 50 = $32,500

2. Net before interest: $32,500 − $11,000 = $21,500

3. P&I repayment: $250,000 @ 6.0%, 20 years ≈ $1,790/month = $21,480/year
Interest component at start ≈ $15,000

4. Taxable result: $21,500 − $15,000 = $6,500 taxable profit
Tax at 37% ≈ $2,405

5. Cash result (after tax):

• Cash outflows (repayments + expenses): $21,480 + $11,000 = $32,480
• Net before tax: $32,500 − $32,480 ≈ +$20 (roughly cash‑neutral)
• After‑tax: $20 − $2,405 ≈ −$2,385/year (~$200/month cost)

Your cashflow is near neutral, but tax makes it slightly negative because you’re paying tax on the profit while still repaying principal.

4. Comparing the scenarios side‑by‑side

Here’s how these three simplified examples stack up in Year 1.

*Tax at 37% marginal rate. All figures illustrative only.

Use this structure in your own spreadsheet and swap in your numbers. The key is to calculate after‑tax cashflow, not just taxable profit/loss.

5. After‑tax modelling: beyond a simple negative gearing calculator

Most online calculators stop at “annual tax saving”. That’s not enough, especially with the 2026–27 reforms.

How tax really interacts with your cashflow

Your property tax position depends on:

• Taxable rent – after allowable deductions like interest, management, repairs and depreciation.
• Borrowing structure – personal name, company, trust, SMSF.
• Negative gearing rules – especially for established properties bought after May 2026, where losses may be quarantined.
• Your other income sources – salary, business income, dividends. Lenders generally shade or average many of these for borrowing capacity [(/insights/negative-gearing-dividends-business-income-home-loans)].

For a busy professional or business owner, two things really matter:

1. How much extra tax will I pay or save in dollars per year?
2. What does that leave as net monthly cash out of my pocket?

Building your own “after‑tax negative gearing calculator”

In your spreadsheet, add these extra lines:

8. Taxable income from property = Net rent before interest − Interest
9. Marginal tax rate (including Medicare)
10. Estimated tax change = Taxable income × marginal rate (negative if loss, positive if profit)
11. Net after‑tax cashflow = Gross rent − expenses − P&I repayments + estimated tax change

This is close enough for planning, but you should always confirm with your accountant or tax agent before acting.

If you’re self‑employed or have trust structures, read Property strategy for self‑employed and high‑income investors after tax shifts for how the new rules may interact with your business and trust income.

6. Stress‑testing: rate rises, vacancies and income shocks

The property might “just work” based on today’s numbers. Your job is to see if it still works when something goes wrong.

6.1 Interest rate stress test

Model at least three rates:

• Today’s actual rate (e.g. 6.0%)
• APRA‑style buffer of +3% (e.g. 9.0%)
• A middle case (e.g. 7.5%)

Using Scenario B (regional house, $480,000 loan):

• At 6.0%, P&I ≈ $34,500/year, after‑tax cost ≈ $9,669/year.
• At 7.5%, P&I ≈ $39,600/year, interest ≈ $35,900.
  • Taxable loss: $22,500 − $35,900 = −$13,400; tax saving ≈ $4,958.
  • Cash before tax: ($39,600 + $10,000 − $32,500) = −$17,100.
  • After tax: −$17,100 + $4,958 ≈ −$12,142/year (~$1,012/month).

If a 1.5% rise adds ~$200/month to your out‑of‑pocket cost, can you truly afford that on top of home and business commitments?

6.2 Vacancy stress test

Run at least three vacancy assumptions:

• 2 weeks (4%) – good market
• 4 weeks (8%) – softer
• 8 weeks (15%) – tenant trouble or repairs year

Again using Scenario B at 6.0% rate:

• 2 weeks vacancy (base): after‑tax ≈ −$9,669/year
• 4 weeks (48 rented): gross rent = $650 × 48 = $31,200
  • Net before interest: $31,200 − $10,000 = $21,200
  • Taxable loss: $21,200 − $28,800 = −$7,600; tax saving ≈ $2,812
  • Cash before tax: ($34,500 + $10,000 − $31,200) = −$13,300
  • After tax: ≈ −$10,488/year
• 8 weeks (44 rented): gross rent = $28,600
  • Net before interest: $18,600
  • Taxable loss: $18,600 − $28,800 = −$10,200; tax saving ≈ $3,774
  • Cash before tax: ($34,500 + $10,000 − $28,600) = −$15,900
  • After tax: ≈ −$12,126/year

The difference between 2 and 8 weeks’ vacancy is around $2,500/year in extra cost – not catastrophic if you have buffers, painful if you don’t.

6.3 Business and personal income shocks

If you run a small business, you should test any new property against a 30–50% reduction in drawings and higher rates [(/insights/investment-property-strategies-small-business-owners)].

Ask yourself:

• If my business drawings drop 40% for a year, can I still cover:
  • my home loan;
  • this investment’s worst‑case cashflow; and
  • non‑negotiable business overheads?
• Do I have separate buffers – one for the household, one for the business – of at least 2–3 months’ expenses and 1–2 months’ overheads respectively?

If the honest answer is “no”, your first move probably isn’t buying another geared property. It’s building buffers, as discussed in How to Weigh Business Expansion Against Buying an Investment Property.

For business owners, property decisions must fit safely around business cashflow and buffers.

7. One‑week action plan: get decision‑grade numbers

You don’t need to become a full‑time analyst. You do need enough structure that you’re not guessing.

Day 1–2: Gather real inputs

• Shortlist 1–3 properties you’re serious about.
• For each, collect:
  • Recent rental listings and actual rents in the same building/area.
  • Strata reports or body corporate budgets (for units).
  • Council and water rates estimates.
  • Insurance quotes.
  • A realistic repairs allowance (older or regional stock: be generous).
• Check your current loan rates and actual household spending.

Day 3: Build the base model

• Create a simple spreadsheet with one tab per property.
• Implement the 11‑line structure (income, expenses, finance, tax).
• Plug in your numbers for Year 1.
• Note the after‑tax monthly cashflow for each property.

Day 4: Stress‑test and compare

• Add columns for:
  • Rate +1.5% and +3%.
  • Vacancy at 2, 4 and 8 weeks.
• Recalculate after‑tax monthly cashflow for each combo.
• Rank the properties:
  • Best case (today’s assumptions)
  • Base (rate +1.5%, 4 weeks vacancy)
  • Worst (rate +3%, 8 weeks vacancy)

Any property that looks marginal under the base scenario is a warning sign.

Day 5–6: Fit it into your bigger picture

• Add your household budget on another tab:
  • Net income (salary, business drawings)
  • Essential spending
  • Existing loan repayments
• Layer the property’s base and worst‑case cashflow over that.
• Check if your buffers (offset/redraw/savings) can handle:
  • 6–12 months of worst‑case property cashflow; and
  • 3–6 months of household expenses; and
  • 1–2 months of business overheads.

If not, consider scaling back or delaying the purchase.

Day 7: Sanity‑check with a professional

Before committing, get someone who can see tax + loans + business together to sanity‑check your model.

A triple‑qualified adviser (CPA, tax agent and broker) can:

• Check your tax assumptions against the latest Budget reforms.
• Confirm whether your loan structure matches the property use.
• Show you how lenders will view your income, especially if self‑employed.
• Suggest safer structures (separate splits, offset use, SMSF vs personal) where relevant.

8. Special notes for small business owners and self‑employed

If you run a business, your property strategy has to respect your business cashflow first.

Keep these in mind:

• Don’t use working capital as a property deposit – it can weaken both loan approval odds and business resilience, even if the LVR looks fine.
• Avoid using a 30‑year home or investment loan to fund short‑lived business assets – it concentrates risk on your property and usually costs more interest over time.
• If you draw equity from an investment property for business use, structure it as a separate loan split and match the term to the project’s life – cleaner tax and lower long‑run risk.
• Make sure you’ve built distinct household and business cash buffers before taking on another geared property.

For a joined‑up view of business vs property decisions, see Smart investment property strategies for time-poor small business owners.

Key takeaways

• A good cashflow model turns a geared property from a story into a set of clear, after‑tax monthly numbers you can compare with your real life.
• Always model after‑tax cashflow, not just taxable losses or “tax savings”, especially with negative gearing rules tightening from 2026–27.
• Stress‑test every deal against rate rises, vacancies and income shocks before you sign a contract or refinance.
• Small business owners should protect working capital and keep separate buffers for household and business before adding more property leverage.
• A simple spreadsheet and one focused week is usually enough to get decision‑grade clarity on whether a specific property really fits your risk and cashflow.

If you want a second set of eyes on your numbers, book a free 15‑minute strategy call at localknowledge.finance. In one conversation you can cover tax, loan structure and cashflow modelling with a single expert – your tax, your loan, one consultation – and walk away with a clear yes/no on your next geared property move.

General advice only.