Similar to our "Receita Federal", Dale.

 In a month, one has to discover all deductible expenses with medicines, health plans , school fees/tuitions (English courses, for example are not refundable any longer, eons ago to say the truth) and a multitude of others.

  Even, proving that one has all these expenses, you will be refunded only a fraction of the ammount you proved to have had.

   In other words, the tax is calculated over the ammount you earned the previous year (I mean, natural person not legal entities).

   Civil servants, have a monthly discount in their paychecks and they have a slip stating the ammount they received and paid (monthly discounted as I said), this is in which 'a receita' bases to calculate the refund.      Summing up; they pay at the end of every month, the year they work, and are going to be refunded as of the sixth month of the next year, or even till the tenth month.  And just a fraction from what they paid.

  PP.