A limit on the amount of non concessional contributions that can go into super. For the 2014/15 financial year the limit is $180,000, or $540,000 over a 3 year period if under age 65. If you exceed this cap you will enjoy penalty tax of 46.5%. If you have already exceeded your concessional cap (the sister cap to the NCC) and exceed your NCC cap your penalty tax will be 93%. Gulp.