Parliament is sitting under urgency on Friday, grinding its way through the detail of the government's family package bill.

MPs arrived at 9am and parliament can sit until midnight if the bill isn't passed before then - and if it isn't they'll be back on Saturday morning.

The bill is in its committee stage, when its different parts can be debated and there's no time limit.

When it gets through that, there's a two hour third reading debate and then the final vote.

The package was unveiled on Thursday and three hours later the government put parliament into urgency and the first reading debate began.

The Families Package (Income Tax and Benefits) Bill repeals the previous government's tax cuts that are due to come in on April 1 next year.

It implements a raft of pre-election commitments and parts of the government's 100 days plan, including paid parental leave increases and a Best Start tax credit for families with young children.

The bill also reinstates the Independent Earner Tax Credit and increases the Accommodation Supplement.

The government says its combined measures will lift 88,000 children out of poverty.