Cortes of Castile
The Cortes in the Kingdom of Aragon had local assemblies and Ferdinand had to consult all separately.
In Aragon there were two house of nobility; the Greater and the Lesser however, unlike Castile all nobles could attend the Cortes. Ferdinand appointed a justiciar to protect the rights of the people and settle any royal official disputes.
Cortes of Aragon
The Cortes did provide revenue for Ferdinand but they also restricted his power, as all tasks and laws within Aragon had to meet the approval of all the Cortes.
In the Cortes of Valencia, Ferdinand’s powers were further restricted by its three houses that could all consult separately without the monarch in attendance and in the Cortes of Catalonia, the nobles, clergy and town people attended a debate during the Cortes to agree on taxation and legislation. In Catalonia, a disputacian oversaw the navy, army and other parts of the government affecting the region.
As Ferdinand was constantly absent from his kingdom, the Cortes helped oversee all his land, however it can be suggested that they he did not have a supreme power over them because they were able to debate their own law reforms without his consultation and he could not make laws without all the Cortes consent.
Religious sources of revenue
The Church provided the Catholic monarchs with much needed revenue during their reigns, however the Church’s power needed to be contained. The Monarchs wanted the wealth and power of the Church firmly under their control, however the clergy were exempt from taxation and outside the scope of the royal justice system.
Some bishops had even led their dioceses to support Portuguese during the succession wars. Therefore, Isabella saw a necessity for the Church and state in Spain to have an independent relationship with the Church in Rome, so that the Church in Spain would be essentially under her control.
Isabella achieved this, by obtaining Patranoato , the right of provision to bishops ,an accession from the Papacy in 1482, furthermore the Pope accepted her request and granted her the See of Curenca in 1486, which allowed the Monarch of Castile to choose the bishops in Granda. This was successful as once established Patranato is bound to become a royal right however, it can be counter argued that this did not helped to increase Spain’s power during the Catholic Monarchs reigns as it was not enforced until Charles 1 time.
Domestic policy example
Another way in which the Catholic King and Queen aimed to
increase the power of the Spanish government was by targeting
the nobility. Ferdinand removed the Six Evil Customs of Catalonia
in 1486, through the Sentencia de Guadelupe. The customs had
made the remenca peasants bound to the land and their landlords,
however Ferdinand compensated the Lords with money and so
arguably the scheme was successful as the nobles influence in
the rural area were decreased, in addition reducing the influence of nobles at a local level.