About this calculator
The Northern Territory is the only jurisdiction that calculates stamp duty with a formula rather than bands. Up to $525,000 the duty is D = 0.06571441 × V² + 15 × V, where V is the price in thousands of dollars — a curve that starts gently and steepens: about $16,514 on a $400,000 home. Above $525,000 the Territory switches to flat percentages of the full price: 4.95% up to $3 million, 5.75% to $5 million and 5.95% beyond. On a $600,000 Darwin home the duty is $29,700. This calculator applies the formula exactly, then layers your repayment, offset account and LMI on top.
First home buyers get no duty concession in the Territory — the old first-home discount ended years ago — but they get the largest grant in the country instead. The HomeGrown Territory grant pays $50,000 to first-home buyers who buy or build a new home (contracts from 1 October 2024 to 30 September 2027, no price cap), replacing the standard $10,000 First Home Owner Grant while it runs. The one duty exemption that does exist is narrow: a house-and-land package bought from a builder in a single transaction can be duty-exempt under the House and Land Package Exemption, running to 30 June 2027.
How to use it
- Enter the property price and your deposit — the difference, plus any LMI, is the loan amount.
- Add the interest rate and loan term (30 years is the Australian standard).
- If you will keep savings in an offset account, enter the average balance — you will see the interest it saves and how much sooner the loan ends.
- Tick "first home buyer" if it applies: the stamp duty below then uses your state's first-home concessions.
- Read the monthly repayment, the stamp duty and the real payoff time with your offset.
The formula
M is the monthly repayment, P the loan amount, r the monthly rate and n the number of payments. An offset account does not change the repayment; it reduces the balance on which interest is charged, so more of each repayment becomes principal and the loan ends sooner. Stamp duty is charged by the state on the purchase price using that state's banded table.
Worked example
A $600,000 Darwin home with a $120,000 deposit leaves a $480,000 loan. At 6.00% over 30 years the repayment is $2,878 a month and NT stamp duty is $29,700 (4.95% of the price). A first home buyer building new instead would pay the same duty but receive the $50,000 HomeGrown Territory grant. Keep $50,000 in an offset account and the loan ends in 24 years 6 months — 5 years 6 months early — saving about $192,805 in interest.
Sources: Territory Revenue Office stamp duty formula and flat rates (4.95% / 5.75% / 5.95%); HomeGrown Territory grant of $50,000 for first-home buyers of new homes (contracts to 30 September 2027) replacing the $10,000 First Home Owner Grant. Last updated: October 2026.
Frequently asked questions
How much is stamp duty on a $600,000 home in the NT?
$29,700 — above $525,000 the Territory charges a flat 4.95% of the full price. Below $525,000 the formula applies: on $400,000 it gives about $16,514 (an effective 4.13%), and at exactly $525,000 the formula and the flat rate meet at about $25,988.
Do NT first home buyers get a stamp duty discount?
No. The Territory's first-home duty discount ended in 2021 and nothing replaced it. First-home assistance comes as cash instead: the $50,000 HomeGrown Territory grant for new homes (to 30 September 2027), and the standard $10,000 First Home Owner Grant it temporarily replaces. On a new $600,000 build the grant outweighs the $29,700 duty.
What is the HomeGrown Territory grant?
A $50,000 grant for first-home buyers who buy or build a brand-new home in the NT — including owner-builders and off-the-plan — under contracts signed between 1 October 2024 and 30 September 2027. There is no price cap, but every owner must be an eligible first-home buyer, at least one applicant must be an Australian citizen or permanent resident, and you must live in the home for 12 months. It cannot be combined with the separate $30,000 FreshStart grant for non-first-home buyers.
What is the NT house-and-land package duty exemption?
If you buy a house-and-land package from a building contractor in a single transaction — the contractor builds or places a detached new home on land it bought from a developer — the purchase can be fully exempt from stamp duty. Contracts must be signed by 30 June 2027 and you must live in the home for at least 6 continuous months starting within 12 months of completion. It is not first-home-specific.
What formula does this home loan calculator — northern territory calculator use?
M = P × r(1 + r)^n ÷ ((1 + r)^n − 1), interest charged on (balance − offset) M is the monthly repayment, P the loan amount, r the monthly rate and n the number of payments. An offset account does not change the repayment; it reduces the balance on which interest is charged, so more of each repayment becomes principal and the loan ends sooner. Stamp duty is charged by the state on the purchase price using that state's banded table. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.