First off, the statute of limitations on tax evasion is 6 years (3 for some tax evasion crimes). So, even if he and his daddy were evading taxes, it is unlikely that Donnie will face criminal charges. However, the government can file a civil suit to get reimbursed if they determine that money is owed.
I think this story clearly blows out of the water Trump's narrative that he got a small loan from his dad and turned it into a billion dollar empire. It also shows why he constantly refuses to release his tax returns.