Punch Taverns' code of practice with tenants has been formerly accredited for clarity under the BIIBAS scheme.
The BIIBAS stamp had already been achieved in principle but formal accreditation comes after Punch sought feedback from its lessees and employees in May.
Changes made since then are minor. For example, more supporting information is supplied in the appendix in areas like guidance on business plans.
The new code is set to be delivered to existing lessees and tenants over the coming months.
Punch Partnerships managing director Roger Whiteside said: "The key principle behind the preparation of our new code of practice was to develop a document that clearly set out the basis for transparent relationships with our partners.
"It's a comprehensive code that covers all areas of our relationship and has been designed in an easy to follow format.
"We wanted to share it with our partners and employees before it was accredited, to make sure that we captured any relevant feedback.
"We recognise that the code of practice is the bedrock of our relationship with our partners and are fully committed to making it live within our business."
Neil Robertson, BII chief executive, said: "This is a robust code that really outlines the fundamentals of Punch Tavern's relationships with its licensees.
"It's a meaty document and it incorporates more than the BBPA [British Beer & Pub Association] Framework Code of Practice, demonstrating a real commitment for positive change in the pub company's interactions with its licensees."
A copy of Punch's accredited code is available from www.biibenchmarking.com.