Privatisations have supercharged NSW finances, with Treasurer Dominic Perrottet set to announce an expected surplus of $4.5 billion for 2016-17 when he delivers his first budget on Tuesday.

The surplus is $500 million higher than forecast in the December half yearly review, which predicted a 2016-17 surplus of $4 billion, thanks to $488.9 million in stamp duty from the partial privatisation of electricity "poles and wires" company Ausgrid.

Since then the 99-year lease of 50.4 per cent of electricity distributor Endeavour Energy and to a lesser extent the 35-year lease of the Land and Property Information service have delivered stamp duty receipts worth more than $700 million.

Mr Perrottet will announce that NSW is on track to become the first state with a net worth of a quarter of a trillion dollars.