Most helpful replyATO Certified Response
Author: Taxduck(Taxicorn)Taxicorn ATO Certified Response8 Nov 2023
If you are a permanent resident, (i.e not a temporary resident) then you should be declaring all income from the UK. Your pension and rental income should be declared on your Australian Tax return in the year you receive it. Any tax paid on that income in the UK can be used to offset the tax that would be assessed on that income here.
This of course depends on your personal details, age, availability of tax offsets such as SAPTO and whether a tax return is necessary because of these.
Try this ATO tool to determine if you need to lodge a tax return
https://www.ato.gov.au/Calculators-and-tools/Do-I-need-to-lodge-a-tax-return/
Any sale of the flat would be regarded as a capital gain event.
Check this link for info on this.
https://www.ato.gov.au/individuals/income-deductions-offsets-and-records/income-you-must-declare/foreign-and-worldwide-income/australian-resident-foreign-and-worldwide-income/