A cat's body being soft does not necessarily mean it is dead; it needs to be determined based on the specific circumstances.
1. A cat that has just died will still have a soft body. This is normal as it has just entered the state of death, and you can still feel its body temperature. A cat's body doesn't immediately stiffen after death; there's a gradual process. Therefore, you can't judge a cat's death solely by whether its body is soft.
2. A cat's body is limp when it appears to be in a state of apparent death. When a cat appears to be in a state of apparent death, it may exhibit weakness in its limbs, purplish mucous membranes, tongue protruding from its mouth, uneven or panting breathing, a rapid but weak heartbeat, and collapse. However, its body will not become stiff. If a cat appears to be in a state of apparent death, the owner should immediately perform CPR and other first aid measures, and take the cat to a veterinary hospital for timely treatment.
3. To determine if a cat is dead, check if it still has a heartbeat. If its heart has stopped beating, it is dead. After a cat has died, its body temperature will continue to drop, and its body will become increasingly stiff. You can also shine a flashlight into the cat's eyes to check for pupil reflex. 
What to do after a cat dies:
1. Take your cat to a pet cremation service center for cremation. This way, you can preserve your cat's ashes as a keepsake. The ashes can be placed in jars or bottles, ensuring proper disposal of the cat's body, preventing contamination, and allowing your cat to continue being with you. Choose a reputable cremation service center.
2. Another option is burial. The pit needs to be dug deep to conceal the cat and prevent other cats from smelling it. You can also sprinkle lime on top to create a cacophony, preventing other animals from smelling it and disturbing the burial site.
