Engineering group WorleyParsons expects a one-time charge of between $45 million and $60 million against its first-half profit following the reduction in the US corporate tax rate.

This charge relates to a reduction in the group’s US deferred tax assets due to the decrease in both the US corporate tax rate and the potential loss of currently available deductions in future years, the company said.

US president Donald Trump last week signed the Republicans’ massive $US1.5 trillion tax overhaul into law, reducing the corporate rate from 35 per cent to 21 per cent.

WorleyParsons shares were untroubled by news of the one-off hit, rising 15 cents, or one per cent, to $14.71 by 1300 AEDT on Wednesday.