For amatrix reportto be eligible as asubreport in a composite report, Workday requires strict alignment between the composite report’s enabled fields and the matrix report’sgroup-by fields. Specifically,every field enabled for filtering and grouping in the composite report must also exist as a group-by field in the matrix report.

If this alignment does not exist, Workday excludes the matrix report from theSub Report Nameselection list because the system cannot reliably aggregate or align the summarized data across reports.

Workday HCM Reporting documentation states:

“When using matrix reports as subreports in composite reports, the group-by fields must align with the composite report’s enabled grouping and filtering fields.”

“Matrix reports that do not meet grouping alignment requirements will not be available for selection as subreports.”

The other options do not control subreport eligibility:

Summarization fields affect calculations, not availability.

Filter alignment is validated later, not at selection time.

Prompt defaults do not determine whether a report appears in the Sub Report Name field.