BGSU Institutional Review Board (IRB) | BGSU IRBNet Portal
These examples are not provided by the BGSU's IRB. Even if you follow these examples, the IRB may still decline to approve your application and may require modifications.
The document at https://www.irbnet.org/release/export/download.jsp?libId=7824 indicates that BGSU's IRB uses a specific definition of "anonymous":
"'Anonymous' should only be used when you do not know who your participants are. An example is an online survey for which participants do not provide any identifying information and you cannot track the identity of participants. 'Confidential' should be used for every other situation. Examples are handing a survey to participants, conducting an interview, or conducting a focus group."
This differs, for example, from the way the Associated Press uses the term.
Consequently in my opinion, it may be best to omit the terms "anonymous" and "anonymity" altogether from your IRB application and from your consent forms. Instead, if your procedure is such that participants can truthfully be told "no one, not even the researchers will know which responses are your responses," then you should just say that rather than use the term, "anonymous." Alternately if the researcher will know things about the participants (for example, if the researcher will have access to a list of those who have participated, or if participants will be asked to identify themselves to receive payment or other incentives), then the term "confidential" should be used instead of "anonymous."
Search for "Human Subjects" at https://gov.ecfr.io/