643. Appeals against taxpayer notice.

Where a taxpayer is given a taxpayer notice, he may appeal against the notice or any requirement therein1. Where a person is given a third party notice, he may appeal against the notice or any requirement therein on the ground that it would be unduly onerous to comply therewith2. Where a person is given a notice requiring information or documents concerning the tax position of an unidentified third party or a third party whose identity can be ascertained3, he may appeal against the notice or any requirement therein on the ground that it would be unduly onerous to comply