commsec t+3 rule, page-19

omb

About 40% of online brokers operate just like comsec in relation to trades/buys following a sale.

The way around it - but a bit risky, is to buy your new stock first and then sell. (in other words, do it in reverse) This way, COMSEC will recognise that you have enough collateral to execute the trade. Make sure though that you dont have any unfilled orders for other stocks as it may reject your trade.

I believe, in your case, you should be able to trade after tomorrow. I dont think you need to wait T+3.

NAB broking is more flexible in this regard in case you're thinking of changing to a different broker.