How I Design Offsets, Splits and Repayments For $3m+ Harbourside Loans

Most people with a $3m harbourside loan think their risk is the interest rate. In my experience, the real risk is a messy structure: one giant loan, one lonely offset, and no plan for how cash moves through the system.

Designing offsets, splits and repayments for a large mortgage is about making sure three things are always true: (1) you can ride out shocks, (2) you don’t accidentally blow up tax deductibility, and (3) you’re not chained to the loan longer than you need to be.

For a $2m–$5m+ harbourside mortgage, that means multiple purpose-based splits, at least two offsets, and repayments set using stressed numbers – not today’s teaser rate. APRA expects banks to use roughly a 3% assessment buffer; you should too.

The mistake I see most on $3m+ harbourside loans

A recent couple in Point Piper had a ~$4.2m home loan. One big split. One offset. Five different purposes rolled into the balance over eight years.

They were:

• Ahead on repayments without knowing how far
• Using redraw like a cheque account
• Mixing home, renovation and investment deposits inside one loan

On paper, they were affluent and safe. In reality, their structure would have been a nightmare if they wanted to upgrade, help kids into the market, or if one of them died.

The fix wasn’t a better rate. It was a better design.

If you take one idea from this article, let it be this: on a large loan, structure beats rate over a 10–15 year horizon. I’ve written about this for Eastern Suburbs borrowers before – the quality of splits, offsets and repayment types often matters more than small rate differences (see /insights/local-bronte-broker-vs-city-franchise).

What “good” looks like for a large harbourside mortgage

Here’s the simple definition I use:

A well‑designed $2m–$5m mortgage has clean splits by purpose, offsets aligned to real‑world risks, and repayments set at a rate 3% above today’s, with 6–12 months of that stressed repayment sitting in cash or offset.

This builds on the guardrails I set out in my guide to managing multi‑million‑dollar loans safely (/insights/design-manage-multi-million-dollar-home-loan-safely) and on safe borrowing limits for high‑net‑worth borrowers (/insights/safe-borrowing-limits-high-net-worth-homeowners).

Let’s break that into three levers you can actually change this week:

1. Offsets – how many, and what are they for?
2. Splits – which purposes need their own loan?
3. Repayment schedule – how hard do you push, and where?

Purpose-based splits and ring-fenced offsets turn a large loan into a controllable system.

1. Offsets: more accounts, not more risk

How many offset accounts make sense on a $3m+ loan?

For a standard mortgage, one offset is usually enough. On a $3m–$5m harbourside loan, I usually want two to four, depending on complexity.

A simple but powerful pattern:

1. Core home offset – linked to the main non‑deductible home split
2. Tax & business offset – for BAS, PAYG, company dividends
3. Opportunity / investment offset – dry powder for opportunities or future equity investments
4. Estate / legacy offset (sometimes) – when we’re deliberately planning for what happens if a high‑net‑worth borrower dies (/insights/large-home-investment-loans-when-high-net-worth-borrower-dies)

The point isn’t complication. The point is ring‑fencing. Money that must not be spent (tax, school fees, estate liquidity) should not sit in the same bucket as money you may invest or spend.

Why offsets beat redraw on big structures

On large loans with mixed purposes (home + future investments), I strongly prefer offsets to redraw. Once cash goes into redraw, every ins and outs starts to matter for tax tracing if you ever convert part of the loan to investment use. This echoes a key rule from my debt recycling guide: use offsets to protect the tax status of deductible debt, not redraw.

Offset vs redraw – what changes on a $3m loan?

• Tax clarity: redraw blurs the original purpose; offsets keep the loan balance “pure”.
• Estate planning: offsets stay in the cash bucket of your estate, not tied to a loan contract.
• Behaviour: it’s psychologically harder to re‑borrow from redraw than to move cash out of offset, which can be good or bad depending on your discipline.

On a $4m home with a $3m loan at 6.5%, every $500k in offset is taking $32,500 a year after‑tax equivalent off your interest bill (because paying down non‑deductible home debt is effectively an after‑tax return equal to the rate).