If the two disagree in a calculation matter, the calculations spelled out in the tax form should be upheld as the gold standard as to which side made the calculation error.
> they had both erroneously tried to apply capital gains tax where it didn't apply at all
Was this issue due to paper tax forms doing a calculation one way, but the IRS's implementation doing it another way?
Most recently, I screwed up by claiming a credit that was not allowed. However, the conditions for it are documented; I was wrong. This is where code could help, in order to clarify obtuse language in the requirements. Obviously, the government runs code which checks the conditions that determine whether a nonzero amount can be claimed in some field, so it's just another calculation. Still, it would be better for that to be crystal clear pseudo-code and not the fragment of some actual implementation.