Since its initial creation of the CSEP certification level, the INCOSE Certification Program required individuals who knew the candidate to submit reference statements confirming the work the candidate had done. These statements had to be made within INCOSE's form and had to come from someone who understood systems engineering well enough to recognize it being performed. 

In recent years, the Certification Program has made it clear that the reference provider (aka, the referent) does not need to be a systems engineer, a CSEP, nor an INCOSE member. This is helpful to those candidates who are the only systems engineer in their organization. The referents do need to understand systems engineering, but that understanding is something they can develop through teaching from the SEP candidate. The referent also doesn't have to be more experienced than the candidate. This is helpful to those who are at the top of their organization and do not have a manager who can write a reference. Peers, clients, and in some cases subordinates are acceptable referents.

Starting in 2020, INCOSE made another change that is directly intended to help non-native speakers of English. Reference submissions used to be required to use text written independently of the candidate's application, with the guidance that it be in the own words of the referent. This was a problem both culturally - as many Americans are accustomed to writing letters of reference for themselves, and then having managers sign them - and for those referents who now found their writing scrutinized for being either too similar to the application text to be independent or too dissimilar to offer corroboration. This unique text is no longer required. Referents may now copy and paste text from the application form. They must add a statement of their own like, "I agree with the text pasted below." 

The most recent change, starting in 2023, was to allow CSEP candidates to submit with as few as 1 referent. The requirement for at least 3 references was removed. The requirement that referents cover at least 5 years of SE experience, including depth and breadth, remains. Some candidates are able to do this with just 1 or 2 referents.

The Certification Program is working toward a goal where references can be shown the application text and initial or otherwise mark to confirm their agreement, without having to write independent statements. That will not occur in 2024 but will be implemented as soon as technology supports it.