of the single joint notice, duplicate originals of the joint notice must be sent by registered mail to each spouse at his last known address. (2) CRoss REFERENCES. - For exceptions to the restrictions imposed by this subsection, see- Subsection (d) of this section, relating to waivers by the taxpayer; Subsection (f) of this section, relating to notifications of mathematical errors appearing upon the face of the return; Section 273, relating to jeopardy assessments; Section 274, relating to bankruptcy and receiverships; and Section 1145, relating to assessment or collection of the amount of the deficiency determined by the Board pending court review. (b) COLLEcITON OF DEFICIENCY FOUND BY BOARD. -If the taxpayer files a petition with the Board, the entire amount redetermined as the deficiency by the decision of the Board which has become final shall be assessed and shall be paid upon notice and demand from the col- lector. No part of the amount determined as a deficiency by the Commissioner but disallowed as such by the decision of the Board which has become final shall be assessed or be collected by distraint or by proceeding in court with or without assessment. (c) FAILURE TO FILE PETITION.-I f the taxpayer does not file a petition with the Board within the time prescribed in subsection (a) of this section, the deficiency, notice of which has been mailed to the taxpayer, shall be assessed, and shall be paid upon notice and demand from the collector. (d) WAIVER OF RESTRICTIONS. -The taxpayer shall at any time have the right, by a signed notice in writing filed with the Commis- sioner, to waive the restrictions provided in subsection (a) of this section on the assessment and collection of the whole or any part of the deficiency. (e) INCREASE OF DEFICIENCY AFTER NOTICE MAmLED. -The Board shall have jurisdiction to redetermine the correct amount of the deficiency even if the amount so redetermined is greater than the amount of the deficiency, notice of which has been mailed to the taxpayer, and to determine whether any penalty, additional amount or addition to the tax should be assessed-if claim therefor is asserted by the Commissioner at or before the hearing or a rehearing. (f) FURTHER DEFICIENCY LETTERS RESTRICTED.- If the Commis- sioner has mailed to the taxpayer notice of a deficiency as provided in subsection (a) of this section, and the taxpayer files a petition with the Board within the time prescribed in such subsection the Com- missioner shall have no right to determine any additionai deficiency in respect of the same taxable vear, except in the case of fraud, and except as provided in subsection (e) of this section, relating to assertion of greater deficiencies before the Board, or in section 273 (c), relating to the making of jeopardy assessments. If the tax- payer is notified that, on account of a mathematical error appearing upon the face of the return, an amount of tax in excess of that shown upon the return is due, and that an assessment of the tax has been or will be made on the basis of what would have been the correct amount of tax but for the mathematical error, such notice shall not be considered (for the purposes of this subsection, or of subsection (a) of this section, prohibiting assessment and collection until notice of deficiency has been mailed, or of section 322 (c), prohibiting credits or refunds after petition to the Board of Tax Appeals) as a notice of a deficiency, and the taxpayer shall have no right to file a petition with the Board based on such notice, nor shall such assess- ment or collection be prohibited by the provisions of subsection (a) of this section. (g) JURISDICTION OVER OTHER TAXABLE YEARS.- The Board in redetermining a deficiency in respect of any taxable year shall con- sider such facts with relation to the taxes for other taxable years as may be necessary correctly to redetermine the amount of such de- INCOME TAX 83
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