Washington: US President Donald Trump on Friday signed the most significant overhaul of the US tax code in 30 years, delivering on a pledge to finish work on the long-standing Republican priority by Christmas.

Trump signed the $1.5 trillion measure in the Oval Office shortly before he was scheduled to head to his Mar-a-Lago resort in Florida for the holidays.

"It's going to a tremendous thing for the American people," Trump said. "It's going to be fantastic for the economy."

He walked through various provisions of the bill, which he touted as "a bill for the middle class and a bill for jobs," adding that "corporations are literally going wild."