Why Do I Have to Pay PAYG Instalments?

The notice arrives, it asks for money you were not expecting to pay, and the obvious reading is that the ATO has decided you owe extra tax. It has not.

PAYG instalments are not a new tax. They are your existing tax bill, paid earlier and in pieces. Every dollar comes straight back as a credit when you lodge. Understanding that changes what the notice means, though it does not change the fact that the first one usually lands at an awkward moment.

What They Actually Are

An employee never sees this problem. Tax comes out of each pay before the money reaches them, so by June the year's tax is already paid. That is PAYG withholding, and it is the employer's job.

Business and investment income arrives untaxed. Without something in between, you would earn all year, spend as you went, and meet the entire bill in one payment months after the money was gone. That is precisely how the old provisional tax system used to catch people out, and PAYG instalments replaced it when the current system came in from 1 July 2000.

So the ATO asks for it quarterly instead, based on what you earned last year. Same tax, different timing.

Instalments are a credit, not a cost. At lodgement, everything you have paid during the year is offset against the assessment. Pay more than you owed and the difference is refunded. The only real question is whether the amount is right.

Why Year Two Hurts

This is the part almost nobody is warned about, and it is the reason the notice feels like a penalty.

In your first year of business, nothing happens. You have not lodged a return yet, so the ATO has no basis to estimate anything, and no instalments are raised. You trade for twelve months with no tax leaving the account.

Then you lodge, and two things arrive at once. The tax bill for that first year, in full, because none of it was prepaid. And the first instalment notice for the year already underway, because your return has now shown the ATO what you earn.

Year two therefore carries roughly two years of tax in the space of a few months. Nothing has gone wrong, the system is simply catching up, but it is a genuine cash flow event and it catches good businesses out. If you are in your first year, this is the thing to put money aside for. Our guide to cash flow problems in small business covers the wider habit.

How You Ended Up in the System

You are not asked and you do not opt in. The ATO enters you automatically once a lodged return shows the right pattern.

For an individual, including a sole trader, all three of these have to be true:

• Instalment income of $4,000 or more on your latest return. This is gross business and investment income excluding GST, not your profit.
• Tax payable of $1,000 or more on your notice of assessment.
• Notional tax of $500 or more, which is the ATO's estimate of the tax on that income for the coming year.

Note the first one carefully. It is turnover, not margin. A business with substantial revenue and slim profit can cross the instalment income test easily, which is why the notice sometimes arrives in a year that did not feel especially profitable.

Companies, trusts and super funds run on different entry rules, generally with a lower bar. If you trade through an entity rather than in your own name, check where it stands rather than assuming the individual thresholds apply.

The Two Options on Your BAS

Instalments appear on your activity statement, or on a separate instalment notice if you are not registered for GST. Most people are offered a choice between two methods, and it holds for the whole financial year, so it is worth a minute's thought rather than paying whatever is preprinted.

Seasonal businesses are usually better off on the rate. A landscaper or a tourism operator paying a flat quarterly amount through their quiet season is funding the ATO out of savings at the worst possible time, when the rate method would have asked for very little.

The trade off is bookkeeping. Option 2 only works if you can produce an accurate income figure each quarter, which means reconciled accounts rather than a guess. If the books are behind, the fixed amount is the safer choice until they are not.

Varying When Your Income Changes

Neither option is fixed. You can vary an instalment up or down when the ATO's estimate no longer matches reality, and the estimate is always at least a year out of date.

Worth varying when:

• Income has dropped. A major client gone, a quiet season, a deliberate wind back. Varying down releases cash you would otherwise get back many months later.
• Income has jumped. Less obvious but just as valuable. Varying up spreads a bill you will owe anyway, instead of meeting it in one lump at lodgement.
• You sold an asset. A property or a parcel of shares can create a capital gain the instalments know nothing about.
• The business structure changed. Incorporating, or ceasing to trade, makes the old estimate meaningless.

The variation has to be lodged on or before the due date for that quarter. You cannot go back and revise one you have already paid, though a later quarter can absorb some of the difference.

Vary on a forecast, not on hope. If your varied instalments come to less than 85 per cent of what you actually end up owing, the ATO can charge a penalty on the shortfall on top of interest. A defensible estimate matters more than an optimistic one.

Sole traders can vary through myGov, entities through Online Services for Business, or your tax agent can do it. The mechanism is easy. Knowing what number to put in it is the part worth advice.

What Underpaying Costs

Skipping an instalment is one of the more expensive ways to borrow money.

Unpaid amounts attract the general interest charge, which compounds daily from the due date. The rate is reset quarterly and sits well above ordinary commercial lending, deliberately so. Check the current rate on the ATO site rather than assuming, because it moves.

There is a second change that makes this materially worse than it used to be. Interest charges incurred from 1 July 2025 are no longer tax deductible. Until then, GIC softened by roughly your tax rate, so a dollar of interest cost well under a dollar after tax. Now a dollar of interest costs a dollar. For an entity that was deducting at 25 or 30 per cent, the same lateness is now something like a third to two fifths more expensive in real terms.

The trap that catches growing businesses is quieter than a missed payment. If you are having a much better year than last year, instalments calculated on last year's figures are too small by definition. Nothing looks wrong, every notice is paid on time, and the shortfall only appears at lodgement. Varying up during the year is the fix, and it costs nothing to do.

Getting Out of the System

If the income that put you in has genuinely gone, you can leave. What you cannot do is simply stop paying.

Where the drop is real and ongoing, the ATO can withdraw you from instalments, usually once a lodged return confirms you are back under the thresholds. Until that happens the obligation stands, so the interim step is to vary the instalments to nil rather than ignore the notices. Ignoring them leaves a debt accruing interest for tax you may not even owe.

Exiting is also not permanent. Cross the thresholds again on a future return and you will be entered again automatically.

Frequently Asked Questions

Do I still lodge a tax return if I pay instalments?

Yes. Instalments are prepayments, not a substitute. The return is where the actual liability is worked out and your instalments are credited against it. Skipping it does not follow from paying instalments, and the lodgement obligation is unchanged.

What if I overpay?

The excess is refunded after you lodge. It is not lost. It has, however, been sitting with the ATO instead of in your account, earning you nothing, which is the argument for varying down when income genuinely falls.

Can I pay monthly instead of quarterly?

Quarterly is standard for most small businesses. Very large instalment income moves you to monthly, and some taxpayers with simple affairs get an annual option. The ATO tells you which cycle applies to you.

I disagree with the amount. What now?

Vary it, before the due date, with a realistic estimate of your income for the full year. There is no need to argue the ATO's figure. It was only ever an estimate based on old information, and varying it is the built in mechanism for exactly this.

Are instalments deductible?

No, and they do not need to be. They are payments of income tax, and income tax is not a deduction against itself. They reduce what you owe at lodgement, which is where the benefit shows up.

Does this apply to rental or investment income?

Yes. Instalment income includes gross investment income, so rent, dividends and distributions all count towards the thresholds. Plenty of people who do not think of themselves as running a business end up in the system through an investment property.

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PAYG instalments are a timing mechanism, not an extra impost. The two things worth actually managing are choosing the method that fits how your income behaves, and varying it when the year stops resembling the one it was based on.

Trew North Accounting reviews instalments for Melbourne small businesses before the quarters land rather than after. See our accounting and tax planning and small business accounting services, or get in touch.

This article is general information, not advice for your circumstances. Thresholds, rates and interest charges change. Check current figures with the ATO or with us before acting.