Gates, who is cooperating with prosecutors in the trial of Trump's former campaign chairman, testified that Manafort directed him to report overseas income as loans in order to lower his taxable income.
Rick Gates has been regarded as a crucial witness for the government ever since he pleaded guilty this year to two felony charges and agreed to cooperate in special counsel Robert Mueller's investigation into possible ties between Russian Federation and the Trump campaign. When a banker asked about $1.5 million debt that Manafort's company owed to a Cyrus entity called Peranova Holdings Limited, Gates produced a backdated document showing it was forgiven. In calling Gates, the government will present jurors with the firsthand account of a co-conspirator expected to say Manafort was knee-deep in an alleged scheme to hide millions of dollars from the IRS and defraud several banks. He told the court he embezzled hundreds of thousands of dollars from his boss.
Similar to prior witnesses, Laporta testified that Gates and Manafort were in lockstep but that Manafort was in charge.
Downing also attempted to show that Gates was the point person in dealing with the accountants.
The witness also testified that he had helped the defendant file false tax returns, and had concealed 15 foreign accounts from the United States government.
Gates said that the foreign accounts were used to receive income they made from their work as political operatives in Ukraine. Gates was Manafort's partner in the consultancy.
His testimony represents the biggest test yet for Mueller's investigation even though this case does not directly play into the issue of alleged cooperation by the Trump campaign in Russian election interference.
Laporta also discussed problems that arose in February 2016 when Manafort needed cash and applied to Citizens Bank for a real-estate loan against property he owned in NY.
Manafort's defense hinges on convincing a jury that it was Gates, not Manafort, who committed all of these crimes, and that Manafort is a victim of Gates.
In questioning Laporta on Monday, a prosecutor asked the accountant about a $10 million (£7.72 million) loan purportedly received by Manafort from Russian businessman Oleg Deripaska in 2006.
Laporta, looking at a summary of loans to Manafort and his businesses, said she could not see any indication that the loan from Deripaska had been paid off.
During that part of Gates' testimony, he said that he lied in a deposition - part of an unrelated case - about the private equity firm run by Manafort's consulting group.
"I was the one who helped organize the paperwork and initiate the wire transfers", Gates said, describing Manafort's use of unregistered Cypriot bank accounts to collect political consulting payments from Ukrainian oligarchs.
Testifying under immunity, she was the first witness to admit she knew accounting manoeuvrers Mr Manafort and Mr Gates requested of her were wrong and could be crimes.
Since the trial started before US District Judge T.S. Ellis last Tuesday, Mr Manafort's lawyers have kept their cross-examinations brief and at times refrained from attempting to rebut damaging testimony in detail.