The Protestant Reformation happened for a reason. Basically, it was to combat the many false teachings that the Roman Catholic Church had adopted through the centuries. When Martin Luther compared Catholicism to Scripture, the result was his nailing the 95 theses to the Wittenberg door. However, instead of reforming the Roman Catholic Church, it resulted in the protesters, the Protestants, who sought to get back to the Scriptures.  The Catholic Church then tried to kill Luther.  But, the Reformation had begun and it spread throughout Europe.

Following is a summarized paragraph with references found in the Catechism of the Catholic Church (CCC) of many of the false teachings of Roman Catholicism. How do we know they are false? By comparing Scripture with what is taught.

The Catholic Church is the one true church (CCC 2105), Infallibility of the Catholic Church, (CCC 2035), Only the Roman Catholic Church has authority to interpret Scripture (CCC 100), The Pope is the head of the church and has the authority of Christ (CCC 2034), The Roman Catholic Church is necessary for salvation (CCC 846), Sacred Tradition equal to scripture (CCC 82), Forgiveness of sins, salvation, is by faith and works (CCC 2036 CCC 2080 2068), Full benefit of Salvation is only through the Roman Catholic Church (Vatican 2, Decree on Ecumenism, 3), Grace can be merited (CCC 2010 CCC 2027), The merit of Mary and the Saints can be applied to Catholics and others (1477), Penance is necessary for salvation (CCC 980), Purgatory (CCC 1031 CCC 1475), Indulgences (CCC 1471 CCC 1478 CCC 1498 CCC 1472), Mary is Mediatrix (CCC 969), Mary brings us the gifts of eternal salvation (CCC 969), Mary delivers souls from death (CCC 966), Prayer to the saints (CCC 2677), The Communion elements become the actual body and blood of Christ (CCC 1374 CCC 1376).

1. The Catholic church is the one true church
   1.  CCC 2105 “The duty of offering God genuine worship concerns man both individually and socially. This is ‘the traditional Catholic teaching on the moral duty of individuals and societies toward the true religion and the one Church of Christ.’ By constantly evangelizing men, the Church works toward enabling them ‘to infuse the Christian spirit into the mentality and mores, laws and structures of the communities in which [they] live.’ The social duty of Christians is to respect and awaken in each man the love of the true and the good. It requires them to make known the worship of the one true religion which subsists in the Catholic and apostolic Church. Christians are called to be the light of the world. Thus, the Church shows forth the kingship of Christ over all creation and in particular over human societies.”
2. Infallibility of the Catholic Church
   1. CCC 2035, “The supreme degree of participation in the authority of Christ is ensured by the charism of infallibility. This infallibility extends as far as does the deposit of divine Revelation; it also extends to all those elements of doctrine, including morals, without which the saving truths of the faith cannot be preserved, explained, or observed.”
3. Only the Roman Catholic Church has the authority to interpret Scripture
   1. CCC 100, “The task of interpreting the Word of God authentically has been entrusted solely to the Magisterium of the Church, that is, to the Pope and to the bishops in communion with him.”
4. The Pope is the head of the church and has the authority of Christ
   1. CCC 2034, “The Roman Pontiff and the bishops are ‘authentic teachers, that is, teachers endowed with the authority of Christ, who preach the faith to the people entrusted to them, the faith to be believed and put into practice.’ The ordinary and universal Magisterium of the Pope and the bishops in communion with him teach the faithful the truth to believe, the charity to practice, the beatitude to hope for.”
5. The Roman Catholic Church is necessary for salvation
   1. CCC 846, “How are we to understand this affirmation, often repeated by the Church Fathers? Re-formulated positively, it means that all salvation comes from Christ the Head through the Church which is his Body: Basing itself on Scripture and Tradition, the Council teaches that the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and Baptism, and thereby affirmed at the same time the necessity of the Church which men enter through Baptism as through a door. Hence they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it.”
6. Sacred Tradition equal to scripture
   1. CCC 82, “…the Church, to whom the transmission and interpretation of Revelation are entrusted, does not derive her certainty about all revealed truths from the holy Scriptures alone. Both Scripture and Tradition must be accepted and honored with equal sentiments of devotion and reverence.'”
7. Forgiveness of sins, salvation, is by faith and works
   1. CCC 2036, “The specific precepts of the natural law, because their observance, demanded by the creator, is necessary for salvation.”
   2. CCC 2080, “The Decalogue contains a privileged expression of the natural law. It is made known to us by divine revelation and by human reason.”
   3. CCC 2068, “so that all men may attain salvation through faith, Baptism and the observance of the Commandments,”
8. The full benefit of Salvation is only through the Roman Catholic Church
   1. “For it is only through Christ’s Catholic Church, which is “the all-embracing means of salvation,” that they can benefit fully from the means of salvation,”  (Vatican 2, Decree on Ecumenism, 3).
9. Grace can be merited
   1. CCC 2010, “Moved by the Holy Spirit and by charity, we can then merit for ourselves and for others the graces needed for our sanctification.”
   2. CCC 2027, “Moved by the Holy Spirit, we can merit for ourselves and for others all the graces needed to attain eternal life, as well as necessary temporal goods.”
10. The merit of Mary and the Saints can be applied to Catholics and others
    1. 1477, “This treasury includes as well the prayers and good works of the Blessed Virgin Mary. They are truly immense, unfathomable, and even pristine in their value before God. In the treasury, too, are the prayers and good works of all the saints, all those who have followed in the footsteps of Christ the Lord and by his grace have made their lives holy and carried out the mission in the unity of the Mystical Body.”
11. Penance is necessary for salvation
    1. CCC 980, “This sacrament of Penance is necessary for salvation for those who have fallen after Baptism, just as Baptism is necessary for salvation for those who have not yet been reborn.”
12. Purgatory
    1. CCC 1031, “The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire:
    2. CCC 1475, “In the communion of saints, “a perennial link of charity exists between the faithful who have already reached their heavenly home, those who are expiating their sins in purgatory and those who are still pilgrims on earth. Between them there is, too, an abundant exchange of all good things.” In this wonderful exchange, the holiness of one profits others, well beyond the harm that the sin of one could cause others. Thus recourse to the communion of saints lets the contrite sinner be more promptly and efficaciously purified of the punishments for sin.
13. Indulgences
    1. CCC 1471, “The doctrine and practice of indulgences in the Church are closely linked to the effects of the sacrament of Penance. What is an indulgence? ‘An indulgence is a remission before God of the temporal punishment due to sins whose guilt has already been forgiven, which the faithful Christian who is duly disposed gains under certain prescribed conditions through the action of the Church which, as the minister of redemption, dispenses and applies with authority the treasury of the satisfactions of Christ and the saints.’ ‘An indulgence is partial or plenary according as it removes either part or all of the temporal punishment due to sin.’ The faithful can gain indulgences for themselves or apply them to the dead.”
    2. CCC 1478, “An indulgence is obtained through the Church who, by virtue of the power of binding and loosing granted her by Christ Jesus, intervenes in favor of individual Christians and opens for them the treasury of the merits of Christ and the saints to obtain from the Father of mercies the remission of the temporal punishments due for their sins. Thus the Church does not want simply to come to the aid of these Christians, but also to spur them to works of devotion, penance, and charity.
    3. CCC 1498, “Through indulgences the faithful can obtain the remission of temporal punishment resulting from sin for themselves and also for the souls in Purgatory.”
    4. CCC 1472, “…On the other hand every sin, even venial, entails an unhealthy attachment to creatures, which must be purified either here on earth, or after death in the state called Purgatory. This purification frees one from what is called the “temporal punishment” of sin…”
14. Mary (there are many false doctrines concerning Mary found in Roman Catholicism, here are a few)     
    1. Mary is Mediatrix, CCC 969, “Therefore the Blessed Virgin is invoked in the Church under the titles of Advocate, Helper, Benefactress, and Mediatrix.'”
    2. Mary brings us the gifts of eternal salvation, CCC 969, “Taken up to heaven she did not lay aside this saving office but by her manifold intercession continues to bring us the gifts of eternal salvation…”
    3. Mary delivers souls from death, CCC 966, “…You [Mary] conceived the living God and, by your prayers, will deliver our souls from death.”
15. Prayer to the saints
    1. CCC 2677, “By asking Mary to pray for us, we acknowledge ourselves to be poor sinners and we address ourselves to the ‘Mother of Mercy,’ the All-Holy One. We give ourselves over to her now, in the Today of our lives. And our trust broadens further, already at the present moment, to surrender ‘the hour of our death’ wholly to her care.”
16. The Communion elements become the actual body and blood of Christ
    1. CCC 1374, “In the most blessed sacrament of the Eucharist “the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained.”
    2. CCC 1376, “The Council of Trent summarizes the Catholic faith by declaring: “Because Christ our Redeemer said that it was truly his body that he was offering under the species of bread, it has always been the conviction of the Church of God, and this holy Council now declares again, that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change the holy Catholic Church has fittingly and properly called transubstantiation.”