Well, considering that the key number is 400% of the poverty level and it's a pretty easy number to look up, it doesn't really seem that your accountant is really on top of the issue. But...if you underestimated your income a lot then even if you income is under 400% of the poverty level you will have to repay a lot of the subsidies for 2017 (doesn't affect 2016 at all), even though probably not all.
