I have an Invoice form to display all of a clinician's billable times per day. This form is not opened directly, but triggered by any one of three different forms where "billable time" work is entered.

Every time a "billable time" work is triggered, the Invoice form is opened but the subform shows only the current entry [record]. One other factor. The main form reads the "billable hours/minutes" and shows the aggregate billable hours total for the day. This "aggregate total" only totals the current, visible record.

When I open the subform separately, I can see all the individual records. Why can't I see the records in the form/subform format?

Is your subform set to continuous forms in properties rather than single form? If set to continuous forms, all related records should show in your subform.