The US president hailed companies for "showering their workers with Christmas bonuses"
Donald Trump has signed a US$1.5tn (€1.26tn) tax cut programme into law.
Although this is the first major overhaul of US tax laws in 21 years, it is far from the "largest tax cut in American history" - a claim repeatedly made by the president in recent days.
It was initially thought that Mr Trump was wait until the new year before signing the package into law, but instead, he decided to make it one of his final items of business before jetting off to his Florida estate for Christmas.
In the Oval Office, he said: "I was going to wait for a formal signing some time in early January - but then I watched the news this morning and they were all saying: 'Will he keep his promise? Will he sign it by Christmas?
"I immediately called downstairs and said 'get it ready'."
Earlier, the president hailed companies "showering their workers with Christmas bonuses" as a result of his corporate tax reforms.
Mr Trump posted a celebratory message on Twitter after big name firms including AT&T and Comcast credited the tax cut programme for allowing them to promise one-off payouts of up to US$1,000 (€843) to hundreds of thousands of workers ahead of the festive season.
Others, such as Boeing, joined them in confirming that the lower tax bills would help them to raise minimum pay and boost investment.
Such announcements deliver an early Christmas present to the president as he looks to bolster his approval ratings among voters and accelerate growth in the economy through higher spending at the same time.
He said on Friday: "Our big and very popular Tax Cut and Reform Bill has taken on an unexpected new source of "love" - that is big companies and corporations showering their workers with bonuses.
"This is a phenomenon that nobody even thought of, and now it is the rage. Merry Christmas!".
News that companies, albeit a small number so far, are passing on benefits of the looming tax changes may help ease jitters among senior Republicans that they risked sparking a political backlash.
Critics of the reforms had warned they would only benefit big corporations and the rich.
The package includes a cut in the corporate rate from 35% to 21%, with about 80% of households due to pay less next year according to an estimate from the Tax Policy Centre.
Another aim of the Trump reforms is that it will encourage America's biggest multinational firms to stop hoarding trillions of dollars offshore and invest the cash at home instead.
Commentators, however, questioned whether those firms announcing benefits for their staff could have broader motives beyond staff morale.
AT&T, for example, could do with some goodwill from the president as he remains a critic of the telecom giant's proposed merger with Time Warner.
The company's chief executive said of the president's legislation: "This tax reform will drive economic growth and create good-paying jobs."