But then, if you're told "tax withheld at source", there's no need to know how to calculate anymore! Why? Because in 2017, we won't pay any tax! But no, elsewhere you'll hear just the opposite: we'll need to know how to calculate well, because in 2017 we'll pay our taxes twice! Neither is true — the Ministry of Finance says so itself: everyone liable for income tax will pay their 2016 tax in 2017. In 2018, once the principle of withholding at source is in place, they will pay their 2018 taxes. Nothing will therefore change for the taxpayer, since their payments will remain uninterrupted. The only change will be for the State, for which there will be no interruption in the collection of tax, but which will ultimately receive no tax revenue for 2017: this will be a "blank year" for it. Everything happens as if the function f, which maps the number of a given year to that of the year for which taxes are paid, showed a change in slope in 2018, but no "gap": as long as n ≤ 2017, f (n) = n – 1, and for n ≥ 2018, f (n) = n.