Processing of return suspended where an assessment notice is issued, and trusts' exemption not applied if classificatory proviso applies. An amendment provides that processing of a return is not necessary where a notice under the statutory assessment notice provision has been issued to the assessee, and inserts a proviso disallowing application of the trusts-and-institutions exemption where a classificatory proviso concerning their status becomes applicable in the relevant previous year, irrespective of withdrawal or rescission of prior approvals or notifications.