Lol - I had the talk with the kids when they were small.   The rule was 1/2 went into savings.  Period.   My youngest decided to challenge this and say it's not fair.   

I said ok, gave him his "paycheck" minus taxes.   heheehehe...he was livid!   I explained to him that if he wanted to treat his money as a paycheck (for doing chores) and he would refuse to save half, then taxes get taken out.    Call if Mommy Government.  

I told him he had to file for a tax refund at the end of the year.   I tell you, to this day, he remembers that lesson.   He never did file for a refund (Uncle Mommy took out about 40% in taxes).  He will save, on his own.  We have no issues anymore.   He's even learned to budget and to plan ahead for expenses.