Euphrasius, the bishop of Poreč, regulates the relations between the Bishopric and the Chapter and prescribes various taxes, including the tithe and the church quartese (a quarter of a tithe) owed by the inhabitants of Poreč and the retainers of church property (forgery composed in the second half of the 12th, or the first half of the 13th century).
Pope Pelagius I writes to a patrician John on the detrimental effects of the schism in the Church (the so-called Three Chapters Controversy), singling out Bishop Euphrasius as a particularly depraved schismatic and advising the patrician to repress the schismatics in the province of Aquileia (that is, the region Venetia et Histria).
The acts of the synod of Grado, heavily interpolated by later falsifications, by which the bishops of the ecclesiastical province of Aquileia remain faithful to the Catholic creed as decreed by the Ecumenical Councils of Chalcedon (451), Ephesus (431), Constantinople I (381) and Nicaea (325), refusing to denounce the Three Chapters condemned by the Second Ecumenical Council of Constantinople (552).
Following the death of Aquileian patriarch Helias, his successor, Patriarch Severus, together with three other bishops (including the bishop of Poreč, John) are imprisoned in Ravenna by the Byzantine exarch Smaragdus; in order to buy their freedom, the prelates agree to condemn the Three Chapters and reunite with Rome, a move that greatly angers other bishops in the ecclesiastical province of Aquileia. Finally, a synod is held in Marano (591) whereby Patriarch Severus is forced to formally acknowledge the error of his ways in supporting the condemnation of the Three Chapters (narrative accounts from Paul the Deacon's History of the Lombards).
The decrees of the Synod of Mantua: the long conflict between the patriarchs of Grado and Aquileia over the metropolitan jurisdiction over Istrian bishoprics is settled in favor of the Aquileian Church.
Patriarch Rodoald donates Rovinj, a land that was destroyed by the "abominable Slavs", to the Bishopric of Poreč. Forged charter.
Emperor Otto II confirms the jurisdictions of the bishops of Poreč and grants them immunities.
A public placitum held in front of the Istrian count Werihen whereby the dispute between the Bishopric of Poreč, represented by Bishop Andrew, and a Bertha, a widow of a Cadoloh, regarding the latter's fiscal obligations towards the Church of Poreč (herbatico and glandatico) is judged in Bertha's favor.
Pope Sergius IV confirms the jurisdictions of the bishops of Poreč over Rovinj, Dvigrad, and Bale that were disputed by the Aquileian patriarch John.
Engelmar, the bishop of Poreč, donates the monastery of Saint Cassian in Poreč to the monastery of Archangel Michael in Pula.
Azica, the daughter of count Wezelin and Williburga, donates properties to the monastery of Saint Mary and Archangel Michael in Lim bay. 14th century forgery.
Countess Williburga, the mother of Azica, confirms her daughters donation and donates even more properties to the monastery of Saint Mary and Saint Michael in Lim. 15th century forgery.
The decision of Henry III's royal court regarding the tithes from the territories of Saint Michael's monastery in Lim bay. 15th century forgery.
Megingaudus, the bishop of Pula, donates a property to St. Michael's monastery, witnessed by "Istrian margrave Ulrich".
King Henry IV (or III) confirms the jurisdictions and immunities of the Bishopric of Poreč.
Henry IV, King of the Romans, donates imperial rights over the Bishopric of Poreč, including the right to appoint and invest its bishops, to the Patriarchate of Aquileia and its Patriarch Henry.
Pope Innocent II confirms the rights and privileges of the incumbent Aquileian patriarch: the metropolitan jurisdiction over sixteen bishoprics, including all the disputed Istrian dioceses, and seven monasteries, grants him the pallium, and corroborates all the possessions and titles of the Aquileian Church, including the "County, the March, the Duchy," the regalian rights and imperial privileges.
Pope Alexander III confirms the spiritual and secular jurisdictions of the bishops of Poreč.
Pope Alexander III confirms the metropolitan jurisdictions of the incumbent Aquileian patriarch, institutes a new suffragan bishopric in Koper, grants him the pallium, and corroborates all the possessions and titles of the Aquileian Church, including the "County, the March, the Duchy," the regalian rights and imperial privileges.
Emperor Frederick I Barbarossa confirms the rights and jurisdictions of the Patriarchate of Aquileia and assumes this church under imperial protection, confirming all the previous donations issued to the patriarchs by his predecessors kings and empires, by the popes, and by other laymen.
The incumbent patriarchs of Grado and Aquileia, Enrico Dandolo and Ulrich of Treffen respectively, solemnly end the centuries-old conflict between the two churches regarding the metropolitan jurisdictions over the Istrian bishoprics: the patriarch of Grado renounces the metropolitan pretensions of his church, the treasury that Patriarch Poppo took from Grado, and the possessions in Marsano, Aquileia, Zèmole and Marano Lagunare, but receives the spiritual jurisdiction over the parishes Latisana and San Fior, together with the quarter of the tithes and the annual income of up to seventy pounds of Veronese coins.
Wolfger, the patriarch of Aquileia and margrave of Istria, confirms the boundaries of the territories under the jurisdictions of the bishops of Poreč. A Forgery drawn up by the chancery of Boniface, the bishop of Poreč (1282 - 1305).
Aquileian Patriarch and Istrian Margrave Wolfger confirms the temporal jurisdictions that the Church of Poreč enjoys by way of donations issued by previous patriarchs of Aquileia; 13th-century forgery.
In the name of Patriarch-margrave Berthold V of Andechs, John de Riva, the general gastald in Istria, orders a Nicholas de Roço of Poreč and all his supporters to present themselves in front of the patriarch in Friuli and to respond to allegations raised against them by a Marino de Mengoso of Poreč and his supporters.