H.B. No. 3521 amends various sections of Article 6243g-4 of the Revised Statutes, which regulates the police officers' public retirement system in certain Texas municipalities. The bill introduces a revised definition of "catastrophic injury," specifying that it must be a duty-related injury from an external event and outlines qualifying conditions. It also clarifies the definitions of "employee" and "salary" to encompass individuals in classified or appointed positions within the police department. Additionally, the election process for board members is modified to require elections before the end of the calendar year, along with new prohibitions on board membership eligibility.

The bill further adjusts pension calculations for members hired before and after October 9, 2004, and establishes guidelines for the Deferred Retirement Option Plan (DROP), detailing how accounts are credited during subsequent service and conditions for resuming pension payments. It introduces provisions for disability pensions, including application timeframes and the board's authority to accept late applications. The bill also clarifies survivor eligibility criteria and pension distribution processes, repeals several sections, and specifies that new provisions will apply only to members retiring or receiving disability pensions after certain dates. The bill is set to take effect on July 1, 2025, pending a two-thirds vote from both legislative houses.