A longtime executive for Donald Trump and the star prosecution witness in the criminal trial of the former US president’s real estate company has been sentenced to five months behind bars for helping engineer a wide-ranging tax fraud at the Trump Organization.

Allen Weisselberg, 75, was expected to be sent to New York’s notorious Rikers Island jail after pleading guilty last August to all 15 counts he faced in an agreement with prosecutors.

The Trump Organization’s former chief financial officer admitted that from 2005 to 2017 he and other executives received bonuses and perks that fraudulently saved the company and themselves money.

Weisselberg admitted evading taxes on $US1.76 million ($A2.56 million) of income. He has paid about $US2 million in taxes, penalties and interest as part of his punishment.

The Trump Organization was convicted last month on all counts it faced at a trial overseen by Justice Juan Merchan in a New York state court in Manhattan.

In sentencing Weisselberg, Justice Merchan said that had the executive not agreed to the five-month term last August in his plea deal, the judge would have imposed a much longer sentence based on the trial testimony.

Justice Merchan singled out Weisselberg for putting his wife on Mr Trump’s payroll so she could receive undeserved Social Security benefits. Other perks for the Weisselbergs included a luxury Manhattan apartment and multiple Mercedes-Benz vehicles.

“The reason the court finds it so offensive is it was driven by greed,” despite Weisselberg’s already “earning over seven figures”, Justice Merchan said.

Though no longer CFO, Weisselberg remains on paid leave from the Trump Organization. Justice Merchan is set to sentence the company on Friday, though penalties are limited to $US1.6 million.

Weisselberg will likely serve 100 days in jail with time off for good behaviour. Those days probably will not be easy. Lying between the New York City boroughs of Queens and the Bronx, Rikers is known for violence, drugs and corruption.

Weisselberg testified that Mr Trump signed bonus and tuition cheques, and other documents at the heart of prosecutors’ case, but was not in on the tax fraud scheme. He also testified that he hoped to get a $US500,000 bonus this month, and that the company is paying his lawyers.

Mr Trump was not charged and has denied wrongdoing.

Manhattan District Attorney Alvin Bragg, whose office prosecuted Weisselberg and the Trump Organization, attended the sentencing. Bragg’s office is still investigating Trump’s business practices.

“In Manhattan, you have to play by the rules no matter who you are or who you work for,” Attorney Bragg said in a statement.

Weisselberg remains a defendant in New York state Attorney General Letitia James’ $US250 million civil lawsuit that accused Mr Trump and his company of inflating asset values and Mr Trump’s net worth.

– AAP