There are caps on the non-concessional contributions you can make each financial year.
From 1 July 2017, the annual non-concessional (after tax) contribution cap was reduced from $180,000 to $100,000 per year. The cap will be indexed in line with the concessional contributions caps.
If you exceed your non-concessional contributions cap in a financial year, you must lodge a tax return for that year, and you may have to pay extra tax.