I don't really agree with that example because of bugs. The rules for how to calculate taxes for a past year don't change, but you probably didn't implement th

I don't really agree with that example because of bugs. The rules for how to calculate taxes for a past year don't change, but you probably didn't implement the previous year's rules perfectly. If you discover a mistake in how you calculated taxes for a previous year, you should recalculate them so that you can file an amendment.