Age last birthday rule is the specific carrier guideline stating that premium rates and eligibility for coverage are based on the insured's age as of their most recent birthday on the policy effective date. The rule explains how to determine insurance age, how backdating or forward-dating affects age calculations, and how exceptions may apply in certain products or jurisdictions. Age last birthday rules exist alongside alternative rules such as age nearest birthday, and carriers disclose which method they use in underwriting manuals and illustration systems. These rules impact competitiveness, particularly for older ages and large face amounts, where a one-year age difference can change pricing and underwriting categories.

Advisors look up the age last birthday rule in carrier materials when planning applications around client birthdays or evaluating whether to backdate a policy to preserve a younger insurance age. Case designers incorporate the rule into side-by-side comparisons, making sure that each carrier's illustration reflects its actual age basis. Occasionally, misunderstandings about the age last birthday rule can lead to surprise premium changes at issue if effective dates shift; advisors prevent this by coordinating closely with new business teams. In advanced markets, age rules may influence which carrier is chosen for large permanent cases, premium financing arrangements, or survivorship designs. Understanding the age last birthday rule helps advisors align application timing, product selection, and illustration accuracy with carrier-specific age conventions.