What changes when you move from Australia to the United States?

Can you just go?

More easily than anyone else. The E-3 is a US work visa for one nationality: "The E-3 classification applies only to nationals of Australia." It is for specialty occupations, and whether a job qualifies is for US Citizenship and Immigration Services and the State Department rather than this guide.

1Before you leave AustraliaLeaving can count as selling your shares and funds, for taxHELP debt: tell the ATO within 7 days of leaving

2ArrivingThe E-3 visa, for Australians onlyHealth insurance is yours to arrange

3Your first US tax yearResident for tax once you pass 183 days, weighted over 3 yearsThen taxed on worldwide income, super included

4Five years as a green card holderMedicare opens to you, to buy into

5If you go homeSocial Security keeps being paid in AustraliaA 401(k) taken before 59½ costs an extra 10%

Before you leave Australia

Australia's tax rules do the most on the way out, so this is the section to read early.

Leaving can count as selling. When you stop being an Australian resident for tax, "you are taken to have disposed of CGT assets for their market value at the time you stopped being a resident, except for any taxable Australian property." Shares and managed funds are treated as sold the day you leave, and any gain goes on that year's return. You can choose instead to "disregard all capital gains and losses when they stop being an Australian resident", which keeps the assets in the Australian tax net until you sell them or come back.

Your home loses its exemption if you sell it after you go. "Foreign residents can't claim the main residence exemption for property sold after 30 June 2020, unless they satisfy the requirements of the life events test", and what counts is when you sign the contract.

A HELP debt comes with you. If you are going for 183 days or more in 12 months, "submit an Overseas travel notification within 7 days of leaving Australia", then report your worldwide income by 31 October each year and repay on the usual thresholds.

Medicare waits for you. An Australian citizen who comes back keeps the right to it: "If you move back to Australia after more than 5 years overseas, you can re-enrol in Medicare."

Super stays. Moving does not change when you can reach it, and how the US taxes it meanwhile is only partly settled.

Your first year in the United States

When the US starts taxing you. A green card makes you resident for tax straight away. Without one, you are resident once you pass the substantial presence test: "31 days during the current year, and" "183 days during the 3-year period", counting all of this year's days, a third of last year's and a sixth of the year before. "The most common dual-status tax years are the years of arrival and departure."

From then on the US taxes your worldwide income. Super, Australian bank accounts and Australian managed funds all come on to US forms, and the FBAR applies once your accounts outside the US together pass $10,000 at any time in the year.

Health insurance is yours to arrange. "Lawfully present immigrants can get Marketplace coverage and may qualify for the premium tax credit", if a job does not provide cover. Medicare later needs a non-citizen to be "An alien lawfully admitted for permanent residence who has resided in the United States continuously for the 5-year period" before buying in.

A credit history starts from nothing. Your Australian record does not follow you. One of the Consumer Financial Protection Bureau's suggestions for starting is a secured card: "You put in an amount of cash, for example $500. Then, you can spend up to that amount on your credit card."

Social Security, with an agreement

This is where Australians do better than New Zealanders. The two countries have a social security agreement, which does three things.

On a posting, you pay into one system, not two: a worker "temporarily transferred to work for the same employer in another country remains covered only by the country from which he or she has been sent", for assignments "expected to last 5 years or less". The Australian employer asks the ATO for a certificate of coverage.

Your records can be added together. Once you have at least six US credits, Australian periods can help you qualify, though "If you already have enough credits under the U.S. system to qualify for a benefit, the U.S. cannot count your Australian credits."

And the payments follow you home: Social Security keeps being paid in Australia, to citizens and non-citizens alike. Your super does not reduce it, and the Age Pension counts it as income.

Children born in the United States

A child born overseas to an Australian citizen can apply for Australian citizenship by descent. It is an application, not automatic, and a parent who is an Australian citizen by descent themselves must have "spent at least 2 years lawfully in Australia" first.

If you go home

US retirement accounts cost more to empty early. Take money from a 401(k) or IRA before 59½ and "Individuals must pay an additional 10% early withdrawal tax unless an exception applies." A plan paying someone no longer resident "must generally withhold 30% of the payment for federal income tax" unless a lower treaty rate is claimed.

Estate tax. Once you have left, and if you are not a US citizen, your estate must file a US estate tax return "if the fair market value at death of the decedent's U.S.-situated assets exceeds $60,000", which includes shares in US companies. Australia is one of the countries with an estate and gift tax treaty with the United States, which New Zealand is not.

A long-held green card has an exit rule. You are a long-term resident "if you were a lawful permanent resident of the United States in at least 8 of the last 15 tax years", and giving up that status can bring in the expatriation tax.

What gets easier, and what gets harder

Easier

• The E-3: a work visa only Australians can get.
• A social security agreement: no double contributions on a posting, and your two records can be added together.
• Social Security keeps being paid if you go home.
• An estate and gift tax treaty, which New Zealanders don't have.

Harder

• Leaving Australia can count as selling your shares and funds, for tax.
• Sell your Australian home once you've left, and the main residence exemption is usually gone.
• Health insurance is on you, and Medicare needs 5 years as a permanent resident to buy into.
• How the US taxes super is unsettled.
• A credit history starts from nothing.

What this guide does not tell you

It does not tell you whether the E-3 or another visa suits you, or how to move to a green card. It does not work out your tax in either country, or whether to defer the capital gains on leaving Australia, which is a question for an adviser in each.

It does not cover state taxes, which differ state by state, or what the tax treaty between the two countries changes for particular income. And how the US taxes super as it grows is a question the IRS has not settled.