Assessing Time Limits: The Time Limits: Excise Duty Limitations
An excise assessment must be made within 12 months of the date when evidence of the facts that justify making the assessment comes to our knowledge.
However, this 12 months evidence of facts time limit is not separate and distinct from the other applicable time limits, see CH51300. You have 12 months from the discovery of the evidence giving rise to the assessment to make that assessment, subject to the other time limits. The evidence of facts rule is a limitation of the other applicable time limits.