Does Masser need to be given from tax return?
If one did not give Maaser on the income when he received it, he is now obligated to give Maaser on this money.
Follow up Question:
What if the return is actually more than what you made, (more than the amount that was reduced from your pay check), but it is being given to you becuase you don’t make so much and have kids?
The amount ‘extra’ (which was not calculated before) is now obligated in Maaser.