'A sliver': don't expect oversized budget windfalls

Any windfall in the mid-year federal budget update is expected to fall well short of revenue upgrades of the past few years.

Treasurer Jim Chalmers has played down the size of revenue write up, citing a slowdown in the jobs market, weaker corporate tax revenue and structural challenges in the Chinese economy dragging down iron ore prices.

"There's still a fair bit of data to land before MYEFO, including national accounts and tax collections, but Treasury's latest estimate is that any upgrade will be a sliver of what we saw in those first four budget updates," Dr Chalmers told parliament on Wednesday.

The average revenue upgrade in the past four budget updates has been $80 billion.