The UPCI accepts the 66-book Protestant canon as the inspired, authoritative Word of God. The deuterocanonical books are not considered canonical Scripture. The UPCI's commitment to Scripture as the supreme authority for doctrine and practice is foundational: all teachings, including the distinctive Oneness theology and Acts 2:38 salvation plan, are presented as the correct biblical exegesis rather than as tradition or innovation.

The UPCI's intense focus on Acts and the epistles of Paul — particularly for its salvation theology and understanding of God — reflects its conviction that the New Testament itself teaches Oneness soteriology. The Acts of the Apostles is especially central: it is the model for how the early church understood and practiced the new birth, and the UPCI regards its distinctive practices as a recovery of apostolic Christianity rather than a deviation from it.

The canonical Scriptures are the final court of appeal for all UPCI teaching. No tradition, creed, or ecclesiastical authority stands above Scripture. This sola scriptura orientation means that UPCI doctrinal claims are presented exegetically — through detailed engagement with biblical texts — rather than through appeal to church councils or patristic consensus.