Required fields are fields that must be completed before a form can be saved or marked complete. They can improve completeness, especially for critical variables such as participant ID, consent status, enrollment date, visit date, primary outcome, or adverse event seriousness.
However, required fields must be used thoughtfully. If too many fields are required, users may enter placeholder values simply to proceed. This can reduce data quality rather than improve it. 
The decision to make a field required should be based on importance and workflow. A field that is essential for participant safety, eligibility, primary analysis, or record linkage may be required. A field that is optional, exploratory, or sometimes unavailable should not necessarily be required. In some cases, the better design is to include explicit coded options such as ‘not done,” “not applicable,” “unknown,” or “participant refused” rather than forcing a value where none exists.
Completion guidelines explain how forms should be completed. They may describe source documents, units, timing, coding rules, how to handle missing information, and how to respond to unusual values. Good completion guidelines reduce variation across staff and sites. They are especially important in multisite studies, where different teams may interpret fields differently.
Completion guidelines can be embedded in REDCap using field notes, descriptive text, or help text, but they should also exist in a study manual or data entry guide. The guide should be used during training and updated when CRFs change. For example, if a field asks for “current medication,” the guideline should specify whether this includes medications taken today, medications prescribed during admission, long-term medications, traditional medicines, or study drugs.
Form completion status should also be defined. REDCap forms often use status indicators such as incomplete, unverified, and complete. The study team should define what each status means. A form marked complete should indicate that data have been entered and reviewed according to study procedures. If staff mark forms complete simply because they reached the end of the form, the status loses meaning.