United States vs Australia After the 2026 Budget: The Honest Comparison

Editor’s note as at 1 June 2026. International tax rules change frequently. Please confirm the current tax rules and their application to your circumstances for any destination that you are seriously considering before making a relocation decision. We can assist with that analysis where required.

Update: since 1 June 2026 the Government has released further detail on the Australian CGT changes. On 18 June 2026 it confirmed the four small business CGT concessions will stay, announced that the turnover threshold for the 50% active asset reduction will rise from $2 million to $10 million from 1 July 2027, and released a consultation paper on a new Innovative Business CGT Concession for eligible startups (founders, employee share scheme participants and early investors). These do not make Australia’s regime equivalent to US QSBS, but founder and small-business exit modelling should be checked against the final enacted law.

Every other destination in this series has a version of the same pitch: come here, pay less tax. The United States is different. Nobody moves to America for the tax.

They move for the market. The biggest economy on earth, the deepest capital pools, the salaries that make Australian packages look like pocket money, and the simple fact that if you’re building a serious technology company, your customers, investors and acquirers are probably already there.

The tax story, though, is much better than most Australians assume. Start with your salary: the US top federal rate of 37% doesn’t begin until USD 640,600 of taxable income for a single filer (roughly AUD 975,000), while Australia takes 47% of everything above AUD 190,000. Married couples can file jointly and effectively average their income across both spouses, something Australia’s strictly individual system has never allowed. Land in a state with no income tax and the average tax rate on a professional salary can run ten or more percentage points below what the same income suffers in Australia. That’s not a rounding error. That’s a house deposit, every single year, for doing nothing except earning the same money somewhere else.

The investment side can be just as friendly. The federal rate on long-term capital gains tops out at 23.8%, roughly half of what a high-income Australian will pay on the indexed gain from 1 July 2027. And for founders, America offers something genuinely extraordinary: the Qualified Small Business Stock rules, which can wipe out federal tax on a USD 15 million exit entirely. Australia has small business CGT concessions, and is consulting on a new Innovative Business CGT Concession for startups, but nothing on the scale of QSBS, as we’ll come to.

On the other hand, the US is the most aggressive tax jurisdiction on this list once it decides you belong to it. Become a US tax resident and you’re taxed on your worldwide income from day one, with a reporting regime that wants to know about every foreign bank account you own. Take a green card and stay too long, and leaving comes with its own exit tax. Take citizenship, and the IRS follows you for the rest of your life, to any country, forever. And your Australian super, which Australia treats with kid gloves, gets treated by the US tax system somewhere between “confusing” and “hostile”.

So this article is a different kind of comparison. Not “how much tax will I save” but “what does the deal actually look like”: the genuinely good bits, the traps that catch Australians every year, and the one immigration advantage Australians have over every other nationality on the planet.

The headline tax position

First, the big structural point. The United States taxes its tax residents on worldwide income. Not territorial like Hong Kong, not remittance-based like Thailand, not foreign-income-exempt like Singapore. Once you’re a US tax resident, your Australian rental income, your Australian dividends, your gains on Australian shares, all of it goes on your US tax return. The US is not a place you go to shelter foreign income. It’s a place you go where the domestic rates happen to be lower than Australia’s.

Start with earned income, because this is where the biggest practical difference lives for most movers. The 2026 federal brackets run from 10% to 37%, and the thresholds are set high by Australian standards: the 37% top rate doesn’t start until USD 640,600 of taxable income for a single filer, or USD 768,700 for a married couple filing jointly. Australia’s 47% top rate (including Medicare levy) starts at AUD 190,000, which is roughly USD 125,000. Same salary, wildly different marginal treatment.

Then there’s the filing trick Australians have never had: married filing jointly. A couple can combine their income on one return with brackets roughly double the single thresholds, which means a single-income or unequal-income household effectively averages its income across both spouses. Australia taxes each individual separately, full stop. For a household where one partner earns USD 250,000 and the other earns little or nothing, joint filing can deliver a structural saving that Australian tax planning simply can’t replicate (though bringing a nonresident spouse into the US system is an election with its own consequences, so it needs checking rather than assuming). Add the standard deduction (USD 16,100 single, USD 32,200 joint in 2026, no receipts required) and the average rate on a professional salary lands well below the Australian equivalent before you’ve done anything clever at all.

For honesty’s sake: US payroll taxes (FICA) take 6.2% for Social Security up to an annual wage base, plus 1.45% for Medicare (2.35% at higher incomes), and employer health insurance premiums function as a shadow tax that Australians don’t budget for. Even after all of that, in the right household fact pattern the average tax rate on the same salary in a no-income-tax state can run materially below the Australian rate, sometimes by ten percentage points or more. The exact gap depends on filing status, state, deductions, payroll taxes, health insurance, the exchange rate, and whether joint filing is available and sensible, so it’s modelling territory rather than a single headline number. For Australians moving primarily to earn, the US is still one of the most effective places on earth to lift your disposable income and compound wealth faster.

Capital gains get their own, lower schedule. Assets held more than one year get preferential federal rates of 0%, 15% or 20% depending on your taxable income. For 2026, a single filer pays 0% up to USD 49,450 of taxable income, 15% up to USD 545,500, and 20% above that. On top sits the Net Investment Income Tax of 3.8% once your income passes USD 200,000 (single) or USD 250,000 (married filing jointly), thresholds that have never been indexed for inflation since 2013 and quietly catch more people every year. So the realistic top federal rate on a long-term gain is 23.8%.

Hold an asset for one year or less and the gain is short-term, taxed as ordinary income at rates up to 37%. The one-year line matters enormously in the US in a way Australians aren’t used to. Our system gives you a concession at 12 months. Theirs gives you a cliff.

Then there’s the state layer. Several states impose no broad-based personal income tax at all: Florida, Texas, Nevada, Tennessee, Wyoming, Alaska, South Dakota. Washington has no general income tax but levies a separate excise on large capital gains, now tiered at 7% rising to 9.9% on gains above USD 1 million, subject to a standard deduction and exemptions (real estate and retirement assets among them). At the other end, California taxes capital gains as ordinary income at rates up to 13.3%. So an Australian founder in Austin pays 23.8% on a long-term gain, and the same founder in San Francisco pays north of 37% once California takes its cut. Same country, wildly different outcomes. Where you land matters almost as much as whether you go.

For completeness: there’s no federal GST or VAT (states levy their own sales taxes), and the FICA payroll taxes described above commonly apply to Australians working in the US. Detached-worker and assignment cases can be affected by the Australia-US social security totalization agreement, so payroll coverage should be checked rather than assumed.

QSBS: the most generous founder tax break in the developed world

Now the genuinely extraordinary bit.

Section 1202 of the US tax code, the Qualified Small Business Stock rules, lets founders and early investors in qualifying C corporations exclude enormous capital gains from federal tax entirely. We called it the single most generous tax provision in the developed world in our main comparison article, and in 2025 Congress made it more generous still.

Here’s how it works after the One Big Beautiful Bill Act, signed into law on 4 July 2025 as Public Law 119-21. For stock issued after that date, in a C corporation with gross assets of USD 75 million or less at issue, originally issued to you (not bought second-hand), in a qualifying active business:

Hold it at least 3 years and you can exclude 50% of the gain. Hold 4 years, 75%. Hold 5 years or more, 100%. The cap on the exclusion is the greater of USD 15 million or 10 times your cost basis, per company. Both the USD 15 million cap and the USD 75 million asset ceiling are inflation-indexed after 2026.

Stock acquired on or before 4 July 2025 stays on the legacy rules. For most modern QSBS acquired after 27 September 2010, that generally means a 100% exclusion after a more-than-5-year hold, capped at the greater of USD 10 million or 10 times basis, with the old USD 50 million gross asset test. Stock acquired in earlier windows can carry a 50% or 75% exclusion instead, a fossil of older versions of the law. Still remarkable, just slightly less so.

Run the numbers on what this means. An Australian founder who builds a company in Australia and sells after 1 July 2027 faces 47% on the indexed gain (where their income puts them at the top rate and no specific concession fully shelters the gain). Australia’s small business CGT concessions, and the proposed Innovative Business CGT Concession for eligible startups, can soften that in the right case, but they come with their own eligibility tests. A founder who builds the same company as a qualifying US C corporation, holds qualifying stock for five years, and sells for a USD 15 million gain pays zero federal tax. Not concessionally taxed. Zero. (State tax can still apply: California, notably, doesn’t conform to the federal QSBS exclusion, which is one more reason founders keep ending up in Texas and Florida.)

The fine print is genuinely fine: original issuance requirements, a domestic C corporation, gross asset limits tested around the time of issuance, an active business requirement during substantially all of the holding period, and exclusions for certain service and investment-style businesses. QSBS planning is a discipline in its own right and the qualification needs to be designed in from incorporation, not discovered at exit. But for an Australian founder with genuine US ambitions, this provision alone can be worth more than every other line in this article combined.

The traps: where the US system catches Australians

Now the other side of the ledger, because the US giveth and the US absolutely taketh away. Four traps, in ascending order of how permanent they are.

Trap one: worldwide taxation arrives faster than you think. You don’t need a green card to become a US tax resident. The substantial presence test catches you on a day-count formula: at least 31 days in the current year, and 183 weighted days across the current year and the two prior years. Some days can be excluded (certain visa categories, medical-condition days, transit days), so it’s not a calculation to do on the back of a boarding pass. Once you’re caught, you’re taxed on worldwide income and dragged into the foreign reporting regime: FBAR filings for your Australian bank accounts, FATCA Form 8938 for foreign assets, and potentially punitive rules for foreign investment funds. Your boring Australian managed funds and ETFs can be classified as PFICs (Passive Foreign Investment Companies), a category the US tax system treats with something close to open contempt: punitive tax rates, nightmarish paperwork, or both. Australians routinely arrive in the US still holding their Australian ETF portfolio and discover the problem two years later. Restructure before you go, not after.

Trap two: your super. Australia treats superannuation as a concessionally taxed retirement vehicle. The US has never formally agreed on what super even is for its tax purposes. Depending on the analysis, your fund can be treated as a foreign grantor trust with annual reporting obligations, and depending on the filing position adopted and the facts involved, some practitioners take the view that fund earnings may be taxable to you before benefits are ever paid, and that employer contributions can be treated as income. The Australia-US tax treaty, signed in 1982, predates compulsory super and gives no clean answer. This is one of the most genuinely unresolved areas in Australian-American tax practice, and the difference between a sensible filing position and a careless one can be a great deal of money. If you have a substantial super balance and you’re planning a long US stint, this single issue justifies proper advice on its own.

Trap three: the green card. A green card can make you a US tax resident under US domestic law, and once that status starts it generally continues until it is formally abandoned, revoked or judicially terminated, regardless of where you actually live. (If the green card is granted while you’re outside the US, the residency start date is generally your first day of presence in the US as a lawful permanent resident.) And here’s the part most people learn too late: hold a green card for 8 of the last 15 years and you become a “long-term resident”, which means that when you eventually give it up, you can be treated as a covered expatriate under section 877A and hit with an exit tax, a deemed sale of your worldwide assets on the way out. Sound familiar? It’s CGT Event I1 with an American accent, except you may have already paid the Australian version on the way in. The green card is a wonderful thing if America is genuinely your long-term home. It’s an expensive souvenir if it isn’t. Don’t take one casually.

Trap four: citizenship. The United States is essentially the only major country on earth that taxes its citizens on worldwide income regardless of where they live. Naturalise as a US citizen and the IRS is in your life permanently: annual returns, FBARs and FATCA filings forever, whether you’re living in New York, Noosa or Nepal. Renouncing later costs money, paperwork, and potentially the same section 877A exit tax. Plenty of Australians take US citizenship with their eyes open and never regret it. But it is the single most binding tax decision you can make, and it deserves to be treated that way.

And one bonus trap that catches Australians who never even move: the US estate tax. A non-domiciled foreigner gets an exemption of just USD 60,000 on US-situs assets, taxed at rates up to 40% above that. US-situs assets include shares in US companies held directly. Compare that with the USD 15 million exemption a US citizen or domiciliary gets from 1 January 2026 (set by the same 2025 tax legislation, and indexed after that), and you can see the trap: an Australian with a couple of million dollars of directly held US shares has a latent US estate tax exposure most people have never heard of. The 1953 Australia-US estate tax treaty can improve the position, and structuring can manage it, but it has to be looked at. This applies to Australian investors holding US shares from their couch in Brisbane, not just to movers.

Immigration: the E-3, the visa every other nationality wishes it had

Here’s the genuinely good news, and it’s exclusive to you.

The E-3 visa. Created in 2005 alongside the Australia-US Free Trade Agreement, the E-3 is a work visa available only to Australian citizens. You need a job offer from a US employer, a role that qualifies as a specialty occupation (broadly, professional work requiring a degree), and the credentials to match. That’s it. The annual quota is 10,500 and to date it has never once been filled, so unlike the H-1B (the visa every other nationality fights over in a literal lottery), the E-3 is effectively available on demand to qualified Australians. It comes in 2-year terms, renewable indefinitely, the application is faster and cheaper than an H-1B, and your spouse gets work authorisation. Among every nationality trying to work in America, Australians hold the best hand at the table, and most don’t even know it.

The E-3’s one limitation: it’s a non-immigrant visa, meaning you’re meant to maintain an intention to leave eventually. It doesn’t lead directly to a green card, although plenty of Australians transition via other routes when the time comes.

Other routes, briefly. The E-1 and E-2 treaty trader and investor visas suit Australians running businesses with substantial US trade or investment. The EB-5 investor green card requires roughly USD 800,000 to USD 1.05 million invested in a job-creating enterprise. Employer-sponsored green cards (the EB-2 and EB-3 categories) are the standard long-term route for professionals. And the O-1 covers individuals of extraordinary ability, which is more attainable for accomplished founders and specialists than its name suggests.

The strategic point: the E-3 lets you work in America for years, indefinitely renewed, without becoming a green card holder, which means without walking into trap three. For an Australian who wants the American career and salary without signing up for lifetime entanglement with the IRS, the E-3 plus careful tax residency planning is a combination no other nationality can replicate.

Tax residency and the Australia-US treaty

US tax residency for non-citizens arrives in one of two ways: hold a green card (automatic, regardless of where you live), or meet the substantial presence test, the weighted day-count described above. Note the trap inside the trap: you can be a US tax resident under the day-count while still being an Australian tax resident under our tests. Dual residency in a transition year is common.

The Australia-US double tax agreement, in force since 1983, provides the tie-breaker rules for exactly that situation. The order is unusual and shouldn’t be borrowed from other treaties: first permanent home, then habitual abode, then, if still unresolved, the country with which your personal and economic relations are closer. The treaty also generally reduces dividend withholding tax, typically to 15% for portfolio holdings, with lower rates available in some circumstances for substantial corporate shareholdings and certain qualifying entities, and provides foreign tax credit mechanisms so the same income isn’t fully taxed twice.

The treaty is old, though. It predates compulsory superannuation, FATCA and most of the modern cross-border world, and its gaps (super being the painful one) are where Australian-American tax practice earns its complexity. A clean answer on which country taxes what should never be assumed. It should be checked.

On the Australian side, ceasing Australian tax residency works the same as for every destination: the ordinary residency tests under section 6 of the Income Tax Assessment Act 1936, the ATO’s guidance, and the importance of a clean break. The difference with the US is that some Australians deliberately remain Australian tax residents during a US stint (relying on the treaty to manage the overlap), because becoming a US tax resident has its own costs. Which way to jump depends entirely on your facts: income mix, asset base, super balance, family situation, and how long you genuinely expect to stay.

Leaving Australia: the exit tax, with a twist

When you stop being an Australian tax resident, CGT Event I1 (section 104-160 of the Income Tax Assessment Act 1997) deems you to have sold all your CGT assets at market value on the day you leave, with exceptions for taxable Australian property. Section 104-165 lets you elect to defer instead, keeping the assets in the Australian net so Australia taxes the whole gain when you eventually sell for real.

For the no-CGT destinations in this series, the timing logic is simple: leave early while the growth is ahead of you, pay a small exit tax, and let the future gains accrue tax-free. For America, there’s a twist, because the US will tax your future gains. The choice isn’t between Australian tax and nothing. It’s between Australian tax at 47% on the indexed gain and US tax at up to 23.8% federal (plus state) on gains accruing after you become a US tax resident.

That’s still a big rate difference, roughly half, and for a founder whose company growth is mostly ahead of them, triggering I1 early on a small gain and letting the growth happen under US rates (or, better, inside a QSBS structure where the federal rate on exit can be zero) can be a spectacular outcome. But the modelling has more moving parts than the no-CGT destinations: the state you’ll live in, the QSBS eligibility question, the one-year short-term cliff, the interaction between the I1 deemed disposal and your US cost basis, and the question of whether the US will even recognise the Australian deemed sale for its own basis purposes. This is precisely the kind of cross-border sequencing where the right order of operations is worth real money and the wrong order is just expensive.

The usual rules also apply to anything Australian you keep: the market value cost base rules where assets become taxable Australian property (section 855-45), and the foreign resident capital gains withholding regime on Australian property, now 15% with no minimum threshold since 1 January 2025.

And for clarity, as always: moving to America, even for decades, doesn’t require giving up Australian citizenship. Tax residency and citizenship are separate questions. (It’s the US that blurs them, in the other direction.)

What this looks like for different Australians

The same move plays out very differently depending on who you are.

The founder approaching exit. America is arguably the single best destination on this list for you, and the only one where the destination’s own tax rules can beat zero-CGT countries at their own game. Sell while Australian after 1 July 2027 and 47% of the indexed gain goes to Canberra. Build or restructure into a US C corporation with QSBS qualification, hold five years, and the federal tax on up to USD 15 million of gain (for post-July-2025 stock) is nothing at all. The timing logic still applies: if the growth is ahead of you, leaving early means the Australian exit tax is calculated on a small gain, and the big growth happens inside the QSBS structure. The catches: QSBS must be designed in early, California doesn’t conform, the corporate restructure itself has Australian tax consequences that need handling, and the one-year short-term cliff punishes impatience. Get the sequencing professionally mapped before you incorporate anything.

The high-income earner with a share portfolio. The arithmetic is straightforward: 47% in Australia on the indexed gain after 1 July 2027, versus 23.8% top federal (held over a year) plus your state’s slice. In Texas or Florida, you’re at half the Australian rate. In California, the advantage mostly evaporates. And that’s just the gains: on the salary itself, the higher US thresholds and joint filing typically lift a professional household’s take-home pay well beyond anything a pay rise at home could deliver, which is why the disposable income gap is often what movers notice first. The complications are the portfolio itself: your Australian ETFs and managed funds are probably PFICs and need restructuring before you become a US tax resident, your franked dividends lose their franking value in the US system, and everything you own in Australia becomes annual US reporting homework. The E-3 makes the career move easy. The portfolio needs to be made US-ready before the plane.

The high-net-worth retiree. Honestly, the US is one of the weakest destinations on this list for you. You’d be swapping a 47% rate on Australian gains for US worldwide taxation of your entire income stream, your super sits in tax-treatment limbo, your estate planning collides with a system that taxes non-domiciliaries above USD 60,000 of US-situs assets at up to 40%, and US healthcare costs before Medicare eligibility are a budget line all of their own. Retirees with strong family reasons to be in America make it work with careful structuring. Retirees optimising for tax should look almost anywhere else in this series first.

The family with school-age kids. The E-3 is the family-friendliest visa in this series: your spouse gets work authorisation, the public school system in the right districts is good and free, and the salary uplift for professional couples can be enormous. The costs are healthcare (insurance premiums and out-of-pocket costs that shock every Australian family at first contact), housing in the major coastal job markets, and the compliance load of a two-country financial life. Families who pick their state and school district carefully, and sort health insurance through a strong employer plan, tend to do very well. Families who land in the Bay Area on one income do the maths differently.

The honest list of drawbacks

Beyond the traps already covered, here’s the rest of the ledger.

The compliance burden is the heaviest in this series. Annual federal and state returns, FBARs, FATCA forms, PFIC schedules if you kept the wrong investments, and a tax code that treats your ordinary Australian financial life as exotic. Most Australians in America need a specialist accountant on both sides of the Pacific, every year.

Healthcare is employer-linked and expensive. A good corporate plan makes it invisible. Lose the job, start a company, or retire early, and you discover what American health insurance actually costs.

The one-year short-term gains cliff punishes anyone used to Australia’s gentler 12-month discount line. Sell at 11 months and the gain is ordinary income at up to 37% plus state.

Distance is real. It’s a 13 to 15 hour flight home from the west coast, longer from the east, and the time zones make staying close to Australian family and business interests genuinely harder than from Asia.

And the politics, the litigation culture, and the general intensity of American life are features some Australians love and others find exhausting. You usually know which camp you’re in before you go.

The bottom line

The United States is not a tax haven, and it never pretends to be. It taxes worldwide income, it papers you with reporting obligations, it sets traps for the unwary around super, green cards and citizenship, and its estate tax reaches Australians who never even leave home.

And yet. The salary deal alone, with its high thresholds, joint filing for couples and no-income-tax states, can lift an Australian professional household’s disposable income by more than any promotion they’ll ever win, which makes America one of the best places on earth for an Australian to simply earn, save and compound wealth. The long-term capital gains rate is roughly half of Australia’s post-2027 rate in the right state. QSBS can take a founder’s federal tax on a USD 15 million exit to zero, which no zero-CGT country can beat because zero is zero, except QSBS comes attached to the largest market and deepest capital pool on earth. And the E-3 visa gives Australians an entry ticket every other nationality would queue around the block for.

When you relocate overseas, it’s the things you don’t know that you don’t know that make all the difference financially between a roaring success and simply a change of scenery, same outcome, different country. Nowhere is that more true than America, where the gap between a well-sequenced move and a careless one is measured in PFIC penalties, super misfilings, green card exit taxes and missed QSBS qualifications. The opportunity is real. So is the paperwork. Plan accordingly.

Frequently asked questions

How much is capital gains tax in the United States?

Federal long-term capital gains (assets held more than one year) are taxed at 0%, 15% or 20% depending on income, with the 20% rate applying above USD 545,500 of taxable income for a single filer in 2026. The 3.8% Net Investment Income Tax applies on top once income passes USD 200,000 (single), making the realistic top federal rate 23.8%. Short-term gains are taxed as ordinary income at up to 37%. State tax comes on top and ranges from zero (Florida, Texas and others) to 13.3% (California).

Is income tax lower in the United States than in Australia?

For many working Australians, yes, often substantially. The US top federal rate of 37% starts at USD 640,600 of taxable income for a single filer in 2026 (roughly AUD 975,000), against Australia’s top marginal rate applying from AUD 190,000. Married couples may be able to file jointly, which can be valuable where one spouse earns significantly more than the other, though the joint-filing decision needs to be checked. In a state with no personal income tax, the average rate on a professional salary can be materially lower than the Australian rate even after payroll taxes, though health insurance and compliance costs belong in any real-world comparison.

What is QSBS and how does it help founders?

The Qualified Small Business Stock rules in Section 1202 let founders and early investors in qualifying C corporations exclude large capital gains from federal tax. For stock issued after 4 July 2025, holding for 3, 4 or 5 years excludes 50%, 75% or 100% of the gain, capped at the greater of USD 15 million or 10 times your cost basis per company. Stock issued earlier keeps the old rules: 100% exclusion after 5 years, capped at USD 10 million or 10 times basis. Qualification has strict conditions and needs to be planned from incorporation.

Does the US tax worldwide income?

Yes. US tax residents (citizens, lawful permanent residents once the green card test applies, and anyone meeting the substantial presence day-count test) are taxed on worldwide income, including Australian rental income, dividends and capital gains. The US also taxes its citizens on worldwide income for life, regardless of where they live, which makes taking US citizenship the most binding tax decision an Australian can make.

How can an Australian get a US work visa?

Australians have a unique advantage: the E-3 visa, available only to Australian citizens. It requires a job offer in a specialty occupation and relevant qualifications, comes in 2-year renewable terms, gives your spouse work authorisation, and has an annual quota of 10,500 that has never been filled. Other routes include the E-1/E-2 treaty visas, the O-1 for extraordinary ability, employer-sponsored green cards, and the EB-5 investor green card.

What happens to my Australian super if I move to the US?

This is one of the most unresolved areas in Australian-American tax. The US doesn’t have one clean, settled treatment for Australian superannuation: depending on the fund and the filing position adopted, it may be analysed under foreign trust, foreign grantor trust, or non-exempt employee trust principles, and some practitioners take the view that contributions or earnings may be taxable before benefits are ever paid. Revenue Procedure 2020-17 can remove the Form 3520 and 3520-A reporting for some qualifying foreign retirement trusts, but it doesn’t settle the underlying income-tax treatment or the FBAR and Form 8938 obligations. The 1982 tax treaty predates compulsory super and doesn’t resolve it. Anyone with a substantial super balance planning a long US stint should get specialist advice on this issue specifically.

Do I still pay Australian tax if I move to the US?

It depends on whether you cease Australian tax residency. A clean break means Australia stops taxing your worldwide income, though Australian-source income and Australian property remain taxable here, and leaving triggers CGT Event I1, a deemed disposal of your CGT assets on departure. Some Australians deliberately remain Australian tax residents during a US stint and rely on the Australia-US tax treaty tie-breakers to manage the overlap. Which approach is better depends entirely on your circumstances.