Modifies the senior citizens property tax relief credit

HB 1535 modifies Missouri's senior citizens property tax relief credit program. It directly affects Missouri residents aged 65+ (or 60+ with surviving spouse Social Security benefits), disabled residents, and disabled veterans who served in the military. Key changes include requiring proof of Missouri residency for the full year, clarifying disability definitions, updating income calculations to include certain benefits, and defining "homestead" as the primary residence. The bill also specifies that property taxes must be paid before filing a tax return and adds rules for claiming the credit when a spouse dies during the year.