Donald Trump's supporters have called him a tax code "genius" and he has dubbed himself a "brilliant" manipulator of tax law in the wake of reports that he may have used a billion-dollar business loss to avoid paying federal income taxes for 18 years. But an accountant who used to prepare Trump's business taxes for him said the Republican presidential candidate doesn't even understand the tax code.

Accountant Jack Minick, who prepared the bombshell 1995 Trump tax returns that fell into the hands of the New York Times, said Trump "never saw" his tax returns until they were presented to him for his signature.

"I'm the one who did all the work," Minick said on Inside Edition.

Mitnick also told CNN that Trump had "virtually zero" involvement in the process and said he saw no evidence that Trump was able to "game the tax code" as the Republican presidential candidate has indicated.

He also said Trump didn't have the "patience" to learn about tax provisions.

The Trump camp hasn't admitted that the candidate avoided paying taxes for 18 years, nor has it denied it.

But Trump has since boasted at a campaign rally that he "brilliantly used the tax laws" to his advantage — a phrase repeated by Mike Pence at the vice presidential debate — indicating that the NYT's conclusion about his tax avoidance is accurate.

"I have legally used the tax laws to my benefit and to the benefit of my company, my investors, and my employees," he said. "I mean, honestly, I have brilliantly used those laws."

He added: "I'm working for you now — I'm not working for Trump."