Maybe you guys don't have an income tax? In the US "they" don't calculate my tax. It is up to the me to report all my income, calculate how much tax I owe and then pay it. "They" give us all the forms to fill out but it is up to us to fill out the forms. How they track your income for tax evasion charges is up to the government. They have many ways to do this. Sure you can evade paying the taxes until you get caught.
Perhaps this is part of the confusion? I know many (most?) countries do the calculations and hand over a bill to the taxpayer. In the U.S. we have an unusual system that has the taxpayer prepare their own return. So if you are not used to doing your own taxes it could get quite complicated.
we don't calculate tax we just report our income per year here in italy, you can delcare the false, yes but they are going to check if what you claim is correct or not and if not you are in trouble of course
they calculate the tax based on the income you have, on your job, if you have family, and many other stuff, there rules are different case by case, i think it's the same in usa or sligthly different
still under a certain threshold they don't care, like if you receive 5k only per year, assuming this is true of course, they don't bother taxing you on this, you can ignore and don't claim anything in that document