Query returning empty months

Replace "f.label" with:

trunc(f.efectiva, 'MM')

Label does not exist as a column on the risk_facturas table, it is just an alias and cannot be used in the same query except on the ORDER BY clause. Or you can use it on a higher level (parent) query, like this:

select * from ( select
    null AS NullValue
  , sum(f.comision)         AS value
  , trunc(f.efectiva, 'MM') AS label
from
    risk_facturas f
where
    f.efectiva >= add_months(trunc(sysdate), -13) and f.efectiva < trunc(sysdate) + 1
and f.organizacion_id = :APP_GET_ORGANIZACION_ID
group by
    trunc(f.efectiva, 'MM') ) oq
right join (select trunc(add_months(sysdate,1-level),'mm') d from dual connect by level<14) u
on u.d = oq.label

with t as (
            select  0 comision,
                    trunc(add_months(sysdate,1-level),'mm') efectiva
              from  dual
              connect by level < 14
           union all
            select  comision,
                    trunc(efectiva,'MM')
              from  risk_facturas
              where fefectiva >= add_months(trunc(sysdate),-13)
                and efectiva < trunc(sysdate) + 1
                and organizacion_id = :APP_GET_ORGANIZACION_ID
          )
select  null          NullValue,
        sum(comision) value,
        efectiva      label
  from  t
  group by efectiva
  order by efectiva
/

SY.

-- correction: f. is removed