Limitations.—

Sec. 312. Limitations.— (a) Except as otherwise provided in this section, the amount of any tax imposed by this title shall be assessed within three years after the deed is recorded by the Commissioners and no proceeding in court without assessment for the collection of such tax shall be begun after the expiration of such period. (b) In the case of a false or fraudulent return, with the intent to evade tax, the tax may be assessed, or a proceeding in court for collection of such tax may be begun without assessment, at any time. (c) In case of a willful attempt in any manner to defeat or evade the tax imposed by this title, the tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time. (d) In the case of failure to file a return, the tax may be assessed, or a proceeding in court for collection of such tax may be begun without assessment, at any time. (e) Where, before the expiration of the time prescribed in this section for the assessment of the tax imposed by this title, the Commissioners and the taxpayer have consented in writing to its assessment after such time, the tax may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon. (f) The running of the period of limitations provided in this section on the making of assessments, or the collection of the tax imposed by this title in any manner authorized by law, shall be suspended tor any period during which the Commissioners are prohibited from making the assessment or from collecting said tax, and for ninety days thereafter: Provided, That in any case where a proceeding is commenced by a taxpayer in any court in connection with the tax imposed by this title, the running of the period of limitations shall be suspended for the period of the pendency of such proceeding and for ninety days after the decision or the court shall have become final or, if the proceeding shall have been dismissed or otherwise disposed of, for a period of ninety days after such dismissal or other disposition.