National Express Group said an initial assessment of new US tax legislation indicated it would lead to a reduction in the company's effective tax rate from January 1 this year.
The company forecast that the rate would reduce to a percentage point figure in the low 20s, down from a previously anticipated high 20s.
"It is also expected that the measures outlined in the Act will lead to a small tax credit in 2017," the company said. "This is due to the revaluation of deferred tax balances and will be included in the group's 2017 full year results."
National Express said it closed 2017 with a continuation of the positive trading momentum identified in its December trading statement.