(1) Except as provided in Subsections (2) through (4), an assessment is made on the date a liability is posted to the records of the commission.

(2) Except as provided in Subsection (4), for purposes of a liability for which the commission mails a notice of deficiency to a person in accordance with Section 59-1-1405, an assessment is made: (a) if a person has not filed a petition for redetermination of a deficiency under Section 59-1-501, on the date: (i) (A) 30 days after the day on which the commission mails the notice of deficiency to the person; or (B) 90 days after the day on which the commission mails the notice of deficiency to the person if the notice is addressed to a person outside the United States or the District of Columbia; or (ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or (b) if a person files a petition for redetermination of a deficiency under Section 59-1-501, on the date the liability resulting from a final commission decision is posted to the records of the commission.

(a) if a person has not filed a petition for redetermination of a deficiency under Section 59-1-501, on the date: (i) (A) 30 days after the day on which the commission mails the notice of deficiency to the person; or (B) 90 days after the day on which the commission mails the notice of deficiency to the person if the notice is addressed to a person outside the United States or the District of Columbia; or (ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or

(i) (A) 30 days after the day on which the commission mails the notice of deficiency to the person; or (B) 90 days after the day on which the commission mails the notice of deficiency to the person if the notice is addressed to a person outside the United States or the District of Columbia; or

(A) 30 days after the day on which the commission mails the notice of deficiency to the person; or

(B) 90 days after the day on which the commission mails the notice of deficiency to the person if the notice is addressed to a person outside the United States or the District of Columbia; or

(ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or

(A) agrees with the commission on the existence and amount of the liability; and

(B) consents to the assessment of the liability; or

(b) if a person files a petition for redetermination of a deficiency under Section 59-1-501, on the date the liability resulting from a final commission decision is posted to the records of the commission.

(3) Except as provided in Subsection (4), for purposes of a notice of proposed penalty under Section 59-1-302 or Subsection 59-1-401(7), an assessment is made: (a) if a person has not filed a petition for redetermination of a deficiency under Section 59-1-501, on the date: (i) (A) 30 days after the day on which the commission mails the notice of proposed penalty to the person; or (B) 90 days after the day on which the commission mails the notice of proposed penalty to the person if the notice is addressed to a person outside the United States or the District of Columbia; or (ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or (b) if a person files a petition for redetermination of a deficiency under Section 59-1-501, on the date the liability resulting from a final commission decision is posted to the records of the commission.

(a) if a person has not filed a petition for redetermination of a deficiency under Section 59-1-501, on the date: (i) (A) 30 days after the day on which the commission mails the notice of proposed penalty to the person; or (B) 90 days after the day on which the commission mails the notice of proposed penalty to the person if the notice is addressed to a person outside the United States or the District of Columbia; or (ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or

(i) (A) 30 days after the day on which the commission mails the notice of proposed penalty to the person; or (B) 90 days after the day on which the commission mails the notice of proposed penalty to the person if the notice is addressed to a person outside the United States or the District of Columbia; or

(A) 30 days after the day on which the commission mails the notice of proposed penalty to the person; or

(B) 90 days after the day on which the commission mails the notice of proposed penalty to the person if the notice is addressed to a person outside the United States or the District of Columbia; or

(ii) the person in writing: (A) agrees with the commission on the existence and amount of the liability; and (B) consents to the assessment of the liability; or

(A) agrees with the commission on the existence and amount of the liability; and

(B) consents to the assessment of the liability; or

(b) if a person files a petition for redetermination of a deficiency under Section 59-1-501, on the date the liability resulting from a final commission decision is posted to the records of the commission.

(4) In the case of interest under Section 59-1-402 that accrues to a tax, fee, or charge, an assessment is considered to have been made on the date the tax, fee, or charge is assessed.

(5) The commission may at any time within the time period prescribed for assessment under Section 59-1-1410, increase or decrease an assessment if the commission ascertains that the assessment is imperfect or incomplete in a material respect.