Validating data between two sheets to then fill blank cells on one sheet.

Golfstone1121 

Sub incidentreports()

    Dim Name_Incident As Object, Name_incident_missing_report As Range
    Dim i As Long, scriptingKey As String
    Dim resultData
    Set Name_Incident = CreateObject("scripting.dictionary")
    Set Name_incident_missing_report = Range("A2:C" & Cells(Rows.Count, 1).End(xlUp).Row)
        
    resultData = Name_incident_missing_report.Value
    
    For i = LBound(resultData) To UBound(resultData)
        scriptingKey = resultData(i, 1) & "|" & resultData(i, 2)
        Name_Incident(scriptingKey) = resultData(i, 3)
    Next i
    
    Set Name_incident_missing_report = Range("F2:H" & Cells(Rows.Count, "F").End(xlUp).Row)
    resultData = Name_incident_missing_report.Value
    
    For i = LBound(resultData) To UBound(resultData)
        scriptingKey = resultData(i, 1) & "|" & resultData(i, 2)
        If Name_Incident.Exists(scriptingKey) Then _
            resultData(i, 3) = Name_Incident(scriptingKey)
    Next i
    
    Name_incident_missing_report.Value = resultData
    
End Sub

In the attached file you can click the button in cell K2 to run the macro which fills the missing data in column H with the corresponding values from column C.