House Democrats may soon get Trump’s personal tax returns. But what about his business ones?

House Democrats are preparing to challenge Donald Trump’s refusal to release his tax returns—something every other president and presidential nominee has done for decades—but Trump’s personal returns won’t tell the whole story, and some Democrats want to push further. What about his business tax returns?

According to the financial disclosures Trump has been required to file, he has more than 500 different businesses and partnerships, each with its own tax return. His personal taxes would tell how much money he was getting from those, but would not necessarily identify his business partners—a question of particular interest in considering Trump’s Russia ties—or reveal shady tax avoidance tactics on the part of his businesses. 

“If you start with the personal returns, what you’ll run into pretty quickly is a lot of references to investments that don’t tell you very much about what it is,” former IRS Commissioner John Koskinen told Politico. “It’s going to drive you to the business return.”

House Ways and Means Committee Chair Richard Neal has so far proceeded cautiously and deliberately on the matter of Trump’s personal taxes, so it’s extremely unlikely he’ll dive into a demand for the tax information of hundreds of businesses. But if and when Neal gets those personal tax returns, it sure is interesting to think about how Trump’s business taxes could make for some very interesting follow-up.