In the biggest overhaul of the nation's tax code in 30 years, US President Trump has slashed the corporate tax rate from 35 per cent to 21 per cent, boosting the earnings forecast for ASX-listed pokies giant Aristocrat Leisure, which has an extensive slot machine and digital gaming presence in North America.

The bill also adjusts federal income tax brackets, resulting in an uptick in after-tax income from this year. One independent analysis found the average American would pay about $2000 less tax, increasing their after-tax income by 2.2 per cent on average, with bigger increases for the highest earners.

Investment bank Citi said Aristocrat's US earnings accounted for more than 70 per cent of the company's overall earnings, and President Trump's tax cuts would lift its top line.

"We believe that reductions to personal tax rates in the US ... across various income brackets could also bode well for [Aristocrat's] North America segment," Citi analyst Rohan Sundram said.

The personal tax changes are tipped to boost Americans' participation in gambling. Mr Sundram said this could bring a direct benefit for Aristocrat, through greater turnover on slot machines, and indirect benefits, if improved casino revenues prompted operators to roll out more machines on gaming floors.

Citi has updated its earnings per share forecast for Aristocrat to 11 per cent higher than previously expected by 2020.

According to another investment bank, Morgan Stanley, Aristocrat is paying US tax on 36 per cent of its overall earnings, and the lower corporate tax rate would deliver an increase in earnings by 9 per cent a share by the 2020 financial year.

But Aristocrat's US competitors, International Game Technology (IGT) and Scientific Games, which would also benefit from the cuts and stronger balance sheets, may lift their spend on designing and developing new products, as Aristocrat has successfully been doing.

"A quicker repair in balance sheets may see competitor investment increase, too," Morgan Stanley analysts said.

An Aristocrat spokeswoman on Monday said the company derived a "significant proportion" of its earnings from North America.

"Any reduction in US corporate tax rates will be beneficial for our company," she said.

"We are still working through the impact of the changes in detail and will provide more insight as soon as we are in a position to do so."

Aristocrat, earlier this month, completed a $1.3 billion takeover of the US-based Big Fish Games, the creator of several popular mobile and desktop "social casino games" that are played by more than 12.4 million active users every month.

Big Fish, whose catalogue of gaming titles includes Big Fish Casino, Gummy Drop! and Fairway Solitaire, has about 700 employees and five in-house development studios in Seattle and Oakland in the US.