Argument 397: Whether the "Alcabala" Should Be Paid in Barter and Exchange Transactions?(Treatise on Money) (Excerpt‪)‬

According to Castilian law, not only should the alcabala be paid when bartering but it should be paid twice over: one for each of the goods that are bartered. As a matter of fact, each barter operation is considered to be a double sale transaction, (2) one for each of the individuals participating in the barter. For this reason, in Castile, each of the two are required to pay the alcabala according to the value of the good that they receive in exchange for [the one that was given], because each receives it as if it were its price, and, as we all know, in Castile the seller is required to pay the total amount of the alcabala according to the good's price. (3) In Portugal the same requirement to pay the tax exists and, for the same reason already mentioned, it is paid by the two individuals who participate in the transaction. Over there it is called sisa, as da sisa appears in articles. However, each of the individuals pays only half of the tax, because in Portugal, the seller pays half the tax and the buyer the other half, as mentioned when dealing with the buying and selling operation. (4)