If you become a non-resident of Australia you will need to file a tax return to report Australian source income and capital gains where such income is not subject to non-resident withholding tax.

Tax - Income from Employment

Q. Will I have to pay Australian tax in respect of the employment income I will earn overseas?
A. This will depend on your Australian residence status. If you are a non-resident you will not be liable to Australian tax in respect of earnings from an overseas employment.

If you remain tax resident, your foreign source employment income will be exempt from Australian tax providing you work overseas for a period exceeding 90 days and the income is either subject to tax in the country of source or exempt from tax in the country of source for reasons other than the operation of a double tax treaty or a general feature of the source country’s tax law.

While the foreign employment income is exempt from tax, it is taken into account when calculating the tax payable on non-exempt income.

Tax - Other

Q. Will I have to pay tax in respect of Australian investment income earned while overseas?
A. Australian source dividend and interest income received by a non-resident of Australia is not subject to Australian income tax, but to withholding tax only.

Franked dividends are exempt from withholding, unfranked dividends are subject to a withholding of 30%, and interest is subject to a withholding of 10%.

If you remain resident, your investment income will remain subject to Australian tax.

Q. I plan to sell my Australian property while overseas. Are there any capital gains tax implications?
A. The gain from the sale of a “principal residence” is not subject to tax in Australia, unless you are absent from the home for six years and it is rented out.  If the home is not rented, it will remain exempt from capital gains tax indefinitely provided you do not elect another principal residence

Q. Will I remain liable to Australian tax on capital gains tax while outside Australia?
A. If you remain tax resident in Australia you will be liable for tax on gains from the disposal of all assets, worldwide, unless specifically excluded.  If a gain from the disposal of an asset located abroad has already been subject to a foreign capital gains tax, you may be able to claim a credit against Australian tax for the foreign tax paid.

If you are no longer tax resident you are liable to tax on gains from the disposal of specific types of assets that are associated with Australia, known as assets having the necessary connection with Australia.  The liability may be further restricted under the terms of a double tax treaty. 

A special deemed disposal and acquisition rule applies when there is a change in your tax residence status. When you cease to be resident in Australia for tax purposes you are generally deemed to have disposed of all assets acquired since 19 September 1985, other than assets having the necessary connection with Australia, for their market value.  If you become resident in Australia while owning assets acquired after 19 September 1985, other than assets having the necessary connection with Australia, you are deemed to have acquired those assets at the time you become resident at their then market value.

It is possible to elect to override the deemed disposal rule on all affected assets and defer any tax charge until the assets are actually disposed of at some later date following departure.  Furthermore, if you have been resident for fewer than five out of the ten years immediately preceding your departure, you are not deemed to have disposed of any assets owned at the time you became resident, or any assets acquired by inheritance whilst a resident.

Social Security

Q. What Social Security contributions will I pay when abroad?
A. If you are non-resident while abroad, you are not subject to the Medicare levy.

If you remain resident while abroad, you will be subject to the Medicare levy of 1.5% of taxable income while abroad and potentially to the additional Medicare surcharge of 1% if you do not have adequate health cover with an Australian registered fund.

Your employer is required to make the minimal annual Superannuation contributions for you unless:

• Salary or wages are paid to an employee who is not a resident of Australia for work performed outside Australia; and

• Salary or wages paid by an employer who is not a resident of Australia to an employee who is a resident of Australia for work performed outside Australia.

Some employers continue to make Superannuation contributions even though not required.  Ongoing employer contributions may not be tax effective for the purposes of host country taxation if you reside overseas.

Australia is entering into totalisation agreements with a number of other countries e.g. US, the Netherlands, Portugal, which generally seek to avoid double Social Security coverage.  The specific rules of each host country must be reviewed in each case as the outcome can depend on a number of factors e.g. Employer, payroll location etc.
 
Generally, if you leave Australia and are employed by a local entity in the country you are going to, you will be required to pay social security in that country from the start of your employment.