Death appears suddenly in beginning of the movie and repeated two more times, each with a new piece of meaning.
The first time death appeared, it was not just a device to introduce Joe to 22, but started the question "If you die today, what has your life been like?". Joe was not happy with his answer. He had had one calling, jazz, and all this time his life was just leading up to it. He needed a last shot to prove that his life has been worth it by striving back to earth to fulfil this calling.
The second time, death reappeared after Terry, the Great Beyond accountant responsible for the accuracy of number of deaths, caught up with Joe and 22. Death plays two roles here. While it has lit an even stronger desire for Joe to come back, it discouraged 22 to live again as she began to delve into her insecurities. This is such a jarring analogy to what death means to people. Death is a motivator for people with great zeal to do more. And Death is an escape for the many that struggles with purpose and self-love.
The third and final time, death took Joe in when he was in the zone and chose to leave his earthly life to save 22. Death is the beginning for 22 the new soul. Death is a second chance at life for Joe. A new start helps both of them look at life in completely new light. Thanks to Death.
Death is the big question of all living things: Is there anything more after it? The film never explains, but it still narrates through these three meanings that Death can play a part when we're still living, and helps us make sense of all the nuanced feelings we have thinking about Death before. Therefore, we don't need to know what happens after Death to learn from it.