Power to reopen proceedings allows Settlement Commission to reopen completed tax matters with applicant concurrence within a statutory time limit. The Settlement Commission may, if it records written reasons that reopening is necessary or expedient for proper disposal and with the applicant's concurrence, reopen any completed proceeding connected to a pending settlement case and pass such order as it thinks fit, treating the reopened proceeding as if it had been covered by the original settlement application; this authority is subject to a statutory time limitation measured from the date of the settlement application.