Division 293 is an extra 15% tax on concessional super contributions for high-income earners. It exists so the tax break on super isn't worth more to top earners than to everyone else.
When it applies
It kicks in when your "income for surcharge purposes" plus your concessional contributions exceeds $250,000. Income here is broader than taxable income — it adds back things like reportable fringe benefits and net investment losses.
The "lesser of" rule, with an example
The 15% applies to the lesser of (a) your concessional contributions or (b) the amount you're over $250,000. Say you have $260,000 taxable income and $30,000 of contributions: combined income is $290,000, which is $40,000 over the threshold. The base is the lesser of $30,000 and $40,000 = $30,000, so you pay $4,500.
How you pay it
The ATO issues a Division 293 notice after you lodge. You can pay it personally or release the money from your super fund.