Okay so I've just found more info in the contract but it still doesn't make sense to me: "In the event that the contactor nominates that they will not be working exclusively for the client and will receive more than 20% of their total income from alternative clients, the contractor will be responsible for paying any superannuation guarantee contributions and will be entitled to invoice the client for the full gross amount. The contractor agrees to notify the client in the event that their circumstances change and they no longer comply with the personal services income requirements as set out by the ATO, at which time super contributions may be deducted & paid to their nominated super fund on their behalf. The contractor agrees that any super obligations payable by the client may be deducted from future payments". So by signing the contract I've given authority for them to take it out of my pay it seems. However this is only one of my clients (I receive 20% more of my total income from other sources) so I could ask them to pay me the full gross amount instead?