They obviously can write the software. We know this because they already written it. We know this because when you e-file if your tax return is one of the ones

They obviously can write the software. We know this because they already written it. We know this because when you e-file if your tax return is one of the ones for which they don't actually need any information you provide and you made a mistake they tell you right then what your mistake is and reject the filing.