IIRC, Trump became CEO of his Dad's company in 1973 and had worked for the company before that, so the IRS has probably been auditing Trump's taxes more or less every year or three since the early 70s or late 60s.
A private company the size of the Trump Organization also have a slew of internal accountants who audit their own taxes. Additionally, if the Trump Org. did ANY business with the government (involving over 750k) they would be subject to an annual A-133 audit.
President Trump was apolitical and ambiguous in his political leanings until he ran for President in 2015. It is difficult to determine or know if the company had been audited frequently by the IRS, nor #45 personally. All speculation, which libs enjoy doing.