Montana Title 19. Public Retirement Systems § 19-19-502. Disability retirement allowance

(1) A police officer who is eligible under 19-19-402 before completing 20 years of service must receive a sum equal to one-half the base salary, excluding overtime and payments in lieu of sick leave and annual leave, that the officer was receiving as an active officer computed on the highest salary received in any 1 month during the last year of active service.

(2) A police officer who is placed on the retired list under 19-19-402 and who, at the time of injury or disability, was eligible at the officer's option to be placed on the retired list under 19-19-401(1) or (2) but had elected to serve additional years and was then serving the additional years must be paid for the additional years over the officer's original eligibility at the rate prescribed in 19-19-501(2).