Modern digital instrumentation and controls (I&C) systems incorporate many design features that provide safety and reliability benefits to plant operations. However, design decisions relating to I&C system architecture and implementation of these design features may present challenges to demonstrating safety and compliance to regulatory requirements. There can be significant safety and regulatory impacts from design decisions related the I&C platform used, interfaces among redundant safety divisions and between safety and non-safety systems, deterministic behavior, and diversity strategies. These design decisions may influence the I&C system architecture, result in different hazards and hazard controls (e.g., measures for prevention or mitigation), and affect design complexity, all of which may necessitate corresponding levels of evidence (i.e., level of detail, analysis, testing, operating experience, etc.) to demonstrate that the I&C design provides reasonable assurance of safety and compliance with applicable regulatory requirements in an efficient and effective manner. This paper discusses some of the key design decisions for the APR1400 I&C system and architecture and their impact on the Nuclear Regulatory Commission (NRC) staff’s design certification application licensing review. For example, this paper discusses benefits and challenges associated with the I&C platform used for the safety-related I&C system. This paper also explores the challenges associated with non-safety to safety communications and the design constraints chosen that addressed hazards of concern associated with this communication and compliance with the independence design principle and regulatory requirement. In addition, this paper provides examples of information necessary to support the safety and regulatory compliance demonstration. Lastly, this paper provides additional insight on lessons learned during the regulatory process for the APR1400 I&C system design certification application review.