What must be documented according to the Building Code Act?

The correct choice highlights the requirement for documentation outlined by the Building Code Act, which emphasizes the importance of maintaining records as prescribed by regulation. This ensures that there is a clear and consistent method for documenting various aspects of construction and building processes, such as permits, inspections, and compliance with safety standards.

The emphasis on records prescribed by regulation underscores the necessity for accountability and transparency within the construction industry. Such regulations likely stipulate the types of documents that must be kept, how they should be managed, and the duration for which they need to be retained, all of which are critical for effective governance and enforcement of building codes.

In contrast, the other options do not capture the comprehensive requirement set forth by the Building Code Act. Financial transactions and various types of correspondence may be important, but they do not encompass the full scope of documentation mandated by the Building Code. By focusing solely on records as prescribed by regulation, the correct answer aligns with the foundational principles of the Building Code, which aims to ensure safety, compliance, and proper management in construction practices.