Does borrowing against your home for the business affect the main residence CGT exemption?

No, not on its own. Taking a mortgage or caveat over your home to fund the business doesn’t cost you the main residence exemption from capital gains tax. The ATO’s test looks at how the home is used. What can bring part of the home into CGT is running the business from it, with a dedicated business area, as your principal place of business.

This question usually comes up at the kitchen table, often from a spouse who isn’t in the business: “If we borrow against the house, won’t we pay tax when we sell it?” It’s a fair worry. Here’s how the pieces actually fit.

What does the main residence exemption look at?

The main residence exemption is what normally lets you sell your family home without paying capital gains tax. The ATO’s guidance on using your home for rental or business explains that the exemption can be reduced when part of the home is used to produce assessable income, either by renting part of it out or by running a business from it.

The ATO settles this with its interest deductibility test. Picture a loan used to buy the house, real or not. Would the business use of the home let you claim some of that loan’s interest? If so, the same proportion of the home is exposed to CGT. It doesn’t matter whether you actually bought the place with cash or a mortgage; the question is hypothetical.

Notice what the test is about. It’s about the use of the home, imagined as if you’d borrowed to buy it. It isn’t about what other debts the home happens to secure.

And even where business use does count, it’s rarely all or nothing. The ATO describes a partial exemption: when you sell, the part of the home you used to earn assessable income is subject to CGT, and the rest of the home stays exempt. For most owners who simply borrow against the family home, none of it is caught.

Two kinds of interest that people mix up

Most of the confusion comes from two different interest questions living in the same house.

	Interest on a loan to buy the home	Interest on a business loan secured by the home
What the money was for	Buying the home	Funding the business (stock, equipment, tax debt, a purchase)
What decides deductibility	Whether part of the home is used to produce income	What the borrowed money is used for
Effect on the main residence exemption	Central to the ATO’s interest deductibility test	Not part of the test
Typical example	Doctor with a surgery in the house	Builder who borrows against the house to buy a truck

The ATO’s guidance on rental interest expenses shows the same principle from the other side: interest on money used privately isn’t deductible “even if you use your rental property as security for the loan”. The security doesn’t decide the purpose. The use of the money does.

So a home equity business loan is judged, for interest purposes, on the business use of the money. And the home is judged, for CGT purposes, on how the home is used. Different tests, different questions.

When does running the business from home change the CGT picture?

Two things have to be true: the house is the main base for the business, and part of it is kept for that work. Ad hoc days at the kitchen table, or working there because you like it, fall short.

Where it does qualify, the line the ATO draws is about the space:

• Dedicated business premises inside the home, such as a consulting room that’s used for nothing else and couldn’t easily be turned back to family use, can make part of the interest claimable. That’s what brings a slice of the home into CGT.
• A study where you catch up on your regular job usually doesn’t make any interest claimable, so it leaves the exemption alone.
• Choosing not to claim the interest doesn’t help. The ATO says you can’t reduce the gain that way.

Started the business at home after you’d already moved in? Then the cost base is generally reset: you’re treated as buying the home at its market value on the day income-producing use began (relevant where that day falls after 20 August 1996). Sell inside a year of that date and the CGT discount is off the table.

Does a second mortgage or caveat change any of this?

No. A second mortgage or a caveat over your home records the lender’s interest on the title. It doesn’t change how your family uses the house, so it doesn’t feed into the interest deductibility test. The same is true of a first mortgage refinance to release equity, as long as the home itself is used the same way.

Where owners create trouble for themselves is in the record-keeping, not the security:

• Redrawing business money from the home loan mixes private and business purposes in one account. The ATO’s guidance requires apportionment, and the split follows the loan for its whole life.
• Using the business loan partly for private things muddies the deductibility of that loan.
• Moving the business into the house later without noting the date and the space used makes the market value rule hard to apply.

Before you commit, run your plan past your accountant and start a 60-second enquiry to see what the home could support. There’s no credit check to start.

Illustrative example: two owners, two different answers

Illustrative example. Two business owners each borrow $250k against their homes.

The first runs a concreting business from a leased yard across town. He uses the money to buy a second truck and pay out an equipment loan. His home is just his home. The business loan’s interest is assessed on its business use, and the home’s main residence status doesn’t change because it secures the loan.

The second runs a beauty clinic from a purpose-built treatment room at the back of her house, with its own entrance, used only for clients. She borrows to upgrade equipment. Her CGT exposure doesn’t come from the new loan at all. It comes from the treatment room, which she’d set up years earlier. Her accountant has already been tracking that share of the home and had a valuation done when the room opened.

Same loan size, same type of security, completely different CGT positions, because the homes are used differently.

What records should you keep?

A small amount of discipline now saves a lot of argument later:

• A separate loan account for the business borrowing, never a redraw from the home loan.
• A note of what the money was spent on, with invoices or settlement statements.
• If you work from home, a floor plan showing any dedicated business area and the date it started.
• A valuation at the date any income-producing use of the home began, if it applies.
• Your accountant’s advice in writing on how the main residence rules apply to you.

The secured business loans page covers the lending side, and the secured or unsecured tool helps if you’re still deciding whether to use the house at all.

The tax worry’s sorted. Now, what can the equity do?

Once you know a business loan against the house won’t quietly undo the main residence exemption, the real question is the useful one: how much could the home support, and what will the money achieve?

That’s the conversation we have every day. The enquiry takes about 60 seconds and there’s no credit check when you first enquire. We won’t send your details to a pile of lenders, so you won’t be fielding calls from strangers. A real person looks at your home’s rough value, what’s owing on it and what the business needs, then calls you to talk it through. Please answer the form accurately, including whether you run the business from home, so the first option we suggest fits properly.

See what your home equity could fund →