I wouldn't say interop is a huge deal, the main time and cost sink is translating the recursive Gordian knots of tax law into a logically cohesive structure that can be evaluated programmatically. And then you (ideally) must prove its correctness.
Imagine pair programming with a tax lawyer. I'd rather eat my own hands.
DirectFile wasn’t meant to handle complicated edge cases. Most filers have a w2 and a few 1099s, use the standard deduction, and claim a few common credits (e.g., child and earned-income). They could file for free in a few minutes with directfile.
Imagine pair programming with a tax lawyer. I'd rather eat my own hands.