持續進修既tax allowance係指，有啲人佢地去讀多將幾個degree可以享有多啲既免稅額。因為岩岩提到，你所交既稅係由taxable income x average tax rate決定。
由於你既taxable income係gross income - tax allowance，當tax allowance高左，taxable income就會下降。而通常taxable income下降個陣，average tax rate都會不變（if tax system is proportional）或下降（if tax system is progressive），所以你乘出黎交既稅款會低左。