Even during greenfield, you probably fix 5 bugs for every feature. It's just that the bugs you fix were ones you created yesterday and not something a customer reported in the version you shipped a year ago. Writing tax law that even makes people need to think about what is a bug and what isn't is insane. What was wrong with making it simple like (I assume) most countries where you just treat all salaries as expenses that are completely deducted? What would be lost?