Non-inferiority (NI) clinical trials’ goal is to demonstrate that a new treatment is not worse than a standard of care by a certain amount called margin. The choice of non-inferiority margin is not straightforward as it depends on historical data, and clinical experts’ opinion. Knowing the “true”, objective clinical margin would be helpful for design and analysis of non-inferiority trials, but it is not possible in practice. We propose to treat non-inferiority margin as missing information. In order to recover an objective margin, we believe it is essential to conduct a survey among a group of representative clinical experts. We introduce a novel framework, where data obtained from a survey are combined with NI trial data, so that both an estimated clinically acceptable margin and its uncertainty are accounted for when claiming non-inferiority. Through simulations, we compare several methods for implementing this framework. We believe the proposed framework would lead to better informed decisions regarding new potentially non-inferior treatments and could help resolve current practical issues related to the choice of the margin.