There is no universal right answer to whether you pay off debt or invest first, and anyone who hands you one without knowing your numbers is guessing.
What there is, is a filter.
A short set of questions that turns a circular, stressful decision into a fairly mechanical one. Let’s take a look at how it works.
Why This Question Keeps Smart People Stuck
Most people I coach on this are not confused about the arithmetic.
They are stuck because both options feel responsible. Paying down the mortgage feels safe. Investing feels like progress.
So they do a bit of both without deciding, or neither, and the surplus quietly drifts into the everyday account.
That is not a discipline problem. It is a missing decision framework, and once you have one the paralysis usually goes with it.
What Actually Decides Whether You Pay Off Debt or Invest
Four questions, in this order.
Do you have a buffer? – Before either option you need cash you can get to quickly. Without it, one busted hot water system puts the debt straight back on the card.
What does the debt actually cost you? – Not the balance. The interest rate.
Is the interest deductible? – Interest on money borrowed to invest is generally deductible. Interest on your home loan, car loan and credit cards is not, so it is paid out of income you have already been taxed on.
What would you need to earn to beat it? – After tax, after fees, and allowing for the fact that you might not.
Notice what is not on that list. How you feel about debt. What your neighbour did with theirs.
Let’s Run the Numbers
Say you have $20,000 of surplus over the next 12 months, a credit card sitting at 21% and a home loan at 6.2%.
Start with the card. A $20,000 balance at 21% costs you $4,200 a year in interest.
Clear it and you have made a guaranteed 21%, tax free, with no market risk at all. That is roughly $80 a week back in your pocket for doing nothing else.
No investment reliably offers 21%. That one is not a close call.
Now the harder one. The home loan at 6.2% is not deductible, so paying it down saves you 6.2%, guaranteed.
To beat that, an investment has to clear 6.2% after tax.
The tax side of this has just moved. The 50% capital gains discount on assets held longer than 12 months has been removed and replaced with an indexation model, where your cost base is lifted in line with inflation so you are taxed on the real gain rather than the nominal one.
Let’s keep the example conservative and assume no discount.
Say you assume 9% before tax, and treat that as an assumption rather than a promise. On a 39% marginal rate, tax takes about 3.5 percentage points and leaves you roughly 5.5%.
Under indexation the tax generally comes in lower, because the inflation slice of the gain is not taxed. How much lower depends on inflation and your holding period, so run it on your own position rather than mine.
A guaranteed 6.2% from the loan beats a hoped-for 5.5% from the market. Indexation narrows that gap and may well close it.
Let that sit for a minute.
The two options sit within about 1 percentage point of each other. What decided it was the rate and the tax treatment, not how anyone felt about being in debt.
Why a Guaranteed Return Is Worth More Than It Looks
Paying down non-deductible debt is one of the few certain returns available to you.
An expected 9% is a hope with a wide range around it. A 6.2% saved is 6.2% saved, in every market, every year.
That does not automatically make it the better move. It makes it a different kind of move, and that matters most when the gap is this narrow.
When I was digging out of my own hole in my late 20s, I cleared the credit cards first.
Not because the maths was elegant, but because it was the only option where the return was certain and the relief was immediate. I had to get rid of the cards to free up borrowing capacity. Every $10,000 of credit card limit has an approximate $100,000 impact on borrowing power. Let that sink in.
Once they were gone, that same surplus went into the first property. The order mattered more than the speed.
Whether You Pay Off Debt or Invest Is Not a One-Time Decision
The filter is fixed. The answer is not.
At 21% the call is obvious. At 6.2% it is close. If rates fall to 4%, the same person with the same portfolio gets a different answer without having changed their mind about anything.
The capital gains change is the same thing.
You do not build a strategy around a tax setting. You build it around the rate you are paying and the return you can reasonably expect, then let the rules adjust the maths when they move.
So run the filter again whenever something shifts. A rate change, a pay rise, the last card cleared.
In Summary
Whether you pay off debt or invest comes down to four things. Your buffer, the rate, whether the interest is deductible, and what you would need to earn to beat it after tax.
Run that filter and you get a decision you can explain to yourself.
That is what makes it one you will stick to, which matters far more than squeezing out the last percentage point.
Financial confidence is not inherited and it is not a personality trait. It comes from having a process you trust more than your mood on the day.
So, what is the rate on the debt you are carrying right now? If you cannot answer off the top of your head, that is the first thing worth finding out.
Let me know how you have approached this one, leave a comment below.
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