Corporate America brought $US664.9 billion ($938.3 billion) of offshore profits back to the US last year, falling short of the $US4 trillion ($5.64 trillion) President Donald Trump said would return as a result of the 2017 tax overhaul.

US President Donald Trump launched a major tax overhaul in 2017. Credit:AP

Companies repatriated $US85.9 billion in the fourth quarter of 2018, the lowest sum for the year and down from $US100.7 billion the previous quarter, Commerce Department data showed. Corporations brought back $US579 billion in the first three quarters of 2018, upwardly revised from $US571.3 billion in the prior report.

Corporations are bringing back more than they did in 2017, before the tax law was enacted, when US firms repatriated $US155.1 billion.

Companies kept much of their overseas profit offshore because a 35 per cent tax kicked in only if they brought the cash back to the US But the Republican tax law set a one-time 15.5 per cent tax rate on cash and 8 per cent on non-cash or illiquid assets, regardless of the country where the profits sat.