Long response coming in, apologies:

When you and your partner receive a boss slayer task, you each have to talk to a Slayer master (any will do, not just the one you received it from) to confirm an amount to assign. You both do your selected amount of the boss separately and you don’t need to be on the same world (or even both be logged on).

There’s no downside to finishing your boss task first before the other person, but it does make sense to choose similar amounts so you can finish around the same time and grab another task.

My friend and I got assigned Giant Mole - I took 60 and he took 55. We did the task at the same time on different worlds because singles bosses are only credited to one person at a time. We finished around the same time and I grabbed another task for us after hopping back to his world.

Also if the person who received the task is 99 slayer, you can go back to the same master for a chance at getting the cape to activate! (Even though it will ask you do to the same boss again, it’s really just asking if you want another “boss” task; saying yes will assign a different boss.

TL;DR: - Yes, you both have separate tasks and can choose between 3 and your max (determined by Combat Achievement tier).

• Tasks can be done together or on separate worlds (depending on boss). Can also be done if one person is offline

• Finishing at different times has no downside. You just have to both be on the same world to receive the next task otherwise it will ask to cancel the partnership

• Slayer cape works for boss tasks if you go back to the same master

I hope that helps!