Section 57-38-39 - Deficiency, protest, and appeal1. When tax is understated on a return because of a mathematical or clerical error, the tax commissioner shall notify the person of the nature of the error and the amount of additional tax due. This notice is not a notice of deficiency and the person has no right to protest.2. If upon audit the tax commissioner finds additional tax due, the tax commissioner shall notify the person of the deficiency in the tax payment. Such notice of deficiency must be sent first-class mail and must assess the amount of additional tax due and set forth the reasons for the increase.3. A person has thirty days, ninety days if the person is outside the United States, to file a written protest objecting to the tax commissioner's assessment of additional tax due. The protest must set forth the basis for the protest and any other information which may be required by the tax commissioner. If a person fails to file a written protest within the time provided, the amount of additional tax assessed in the notice of deficiency becomes finally and irrevocably fixed. If a person protests only a portion of the tax commissioner's finding, the portion which is not protested becomes finally and irrevocably fixed.4. If a protest is filed, the tax commissioner shall reconsider the assessment of additional tax due. The reconsideration may include further examination by the tax commissioner or the tax commissioner's representative of a person's books, papers, records, or memoranda. The tax commissioner, upon request, may grant the person an informal conference.5. Within a reasonable time after the protest, the tax commissioner shall mail to the taxpayer a notice of reconsideration and assessment which must respond to the person's protest and assess the amount of additional tax due. The amount set forth in that notice becomes finally and irrevocably fixed unless the person within thirty days commences formal administrative review as provided for in chapter 28-32 by the filing of a complaint.6. Upon written request, the tax commissioner may grant an extension of time to file a protest as provided for in subsection 3 or an extension of time to commence formal review as provided in subsection 5.7. In all cases in which the tax commissioner finds that a person has an obligation to file an income tax return in North Dakota and has failed to do so, the tax commissioner shall notify the person by first-class mail of the tax commissioner's finding and of the remedies provided for in sections 57-38-33, 57-38-45, and 57-38-47. The remedies provided for in the above-listed sections are mutually exclusive and if a person fails to file an income tax return after being notified, the tax commissioner may elect a remedy under which to proceed. If the tax commissioner elects to take the action provided for in section 57-38-33 or subsection 6 of section 57-38-45, the amount so assessed is not reviewable.