The procedure does not apply when the father is a kohen or Levite, and does not normally apply when the mother is the daughter of one.Shulkhan Arukh Yoreh De'ah 305:18 The reason is that the Levites, as substitutes for the first-born, are pledged to minister and assist the kohanim in divine service, and cannot be redeemed from this service obligation.
The procedure does not apply when the father is a kohen or Levite, and does not normally apply when the mother is the daughter of one.Shulkhan Arukh Yoreh De'ah 305:18 The reason is that the Levites, as substitutes for the first-born, are pledged to minister and assist the kohanim in divine service and cannot be redeemed from this service obligation.