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

The years of "rivers-of-gold tax revenue" are "probably behind us", economist Shane Oliver says. (James Gourley/AAP PHOTOS)

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.