ATO debt calculator

Most owners who owe the ATO know the headline figure on the statement. Fewer have added up the plan instalment plus this quarter’s BAS, PAYG and super to see the real monthly drain. Showing that sum is the whole point of this calculator, and it’s the figure that decides whether a plan holds or collapses in month four.

What you enter

The calculator has four inputs, and none of them is an interest rate.

Input	What to put in	Tip
Tax debt owed	The overdue balance across the account you want on the plan	Check the integrated client account in Online services for business, not an old letter
Months to pay	A slider from 3 to 24 months	The ATO looks for the shortest term you can genuinely afford
Estimated interest charges over the plan	A dollar figure from the ATO or your accountant	Leave at 0 to see the debt alone, then add the estimate
New BAS and tax obligations per month	Your average ongoing GST, PAYG withholding and instalments	Quarterly BAS? Divide the usual quarterly bill by three

What the four results mean

Monthly instalment. The debt plus your interest estimate, divided evenly across the months you chose. It’s a planning average: the ATO may set a weekly, fortnightly or monthly schedule, and general interest charge accrues daily on whatever is still owing.

Total tax cash needed per month. The instalment plus your new obligations. This is the honest number. The ATO expects fresh obligations to be met by their due dates throughout the plan, so a plan that only works if this quarter’s BAS slips is not a workable plan.

Total repaid on the plan. The debt plus the interest estimate. Because ATO interest incurred from 1 July 2025 can’t be deducted, this is now the true after-tax cost, which makes it worth comparing with a lender’s total cost on a business loan vs an ATO payment plan basis.

Plan finishes. The month and year the last instalment falls due, counted from today.

A worked example (illustrative)

A Gold Coast joinery business owes $84,000 in overdue activity statements. Its accountant estimates around $6,000 of interest if the debt is cleared over 18 months. Ongoing GST and PAYG withholding average $11,000 a month.

• Monthly instalment: ($84,000 + $6,000) ÷ 18 = $5,000
• Total tax cash needed per month: $5,000 + $11,000 = $16,000
• Total repaid: $90,000
• Plan finishes: April 2028

Now slide the term to 9 months. The accountant’s revised interest estimate falls to about $3,000, so the instalment becomes $9,667 and the monthly tax cash jumps to $20,667. That’s $4,667 more out the door every month in exchange for roughly $3,000 less interest. Whether that trade makes sense depends on the business’s cash runway, which is exactly what our cash runway calculator measures.

Three things this tool can’t see

1. Whether the ATO will accept your term. The ATO decides. Online plans are generally available for debts under $200,000, but the online system handles one plan at a time, and income tax owed is treated separately from activity statement balances.
2. Your lodgement position. Unlodged BAS or returns stall almost every negotiation, with the ATO and with lenders. If anything is outstanding, see business loans when BAS lodgements are late.
3. Escalation risk. A plan that defaults can lead to a garnishee notice or, for company directors, a director penalty notice. Large overdue business tax debts can also be disclosed by the ATO to credit bureaus, which lenders will see later.

Not sure the monthly total is realistic? Ask a specialist to look at the numbers; there’s no credit check just for asking.

When does refinancing beat the payment plan?

Refinancing the debt with a lender tends to be worth a look in four situations:

• The monthly total is above what the business clears after wages and rent, even at 24 months.
• The debt is above the online threshold and the ATO wants a faster schedule than you can carry.
• A plan has already defaulted, and the next step from the ATO is likely to be firmer. Our page on funding an ATO payment plan default covers this.
• Property equity is available, so a secured loan can stretch the repayments well past 24 months.

The trade-off is cost. A lender’s fees and interest are real dollars too, so put both totals side by side. Unsecured lenders will often refinance tax debt for trading businesses with steady bank statements; secured options such as a second mortgage business loan usually cost less over time. For the wider picture, read ATO tax debt business loans. If you’d like free, independent help first, the government-funded Small Business Debt Helpline is listed in the sources on this page.

Related calculators

• Cash flow gap calculator: how big the hole is between paying out and getting paid.
• Cash runway calculator: how many months your cash lasts at today’s burn.
• Business loan repayment calculator: what a refinance loan might cost per week or month.

Tax debt doesn’t have to be a dead end

Plenty of lenders step back as soon as an ATO debt appears. We don’t. Tell us the balance, the monthly figure you could genuinely sustain and whether any property could help. Sixty seconds or so is all the form needs. We don’t pull your credit file to answer an enquiry, and nobody auctions your details to a list of lenders: one specialist reads your numbers and calls you personally. Give us the accurate figures, including anything still unlodged, and the first option we raise will be one that can actually work.

Check my ATO debt options →