Message from God: book 1/204
It is difficult to believe there is still a question about this. I find it hard to imagine. There have been so many reports from thoroughly reliable sources of past life experiences. Some of these people have brought back strikingly detailed descriptions of events, and such completely verifiable data as to eliminate any possibility that they were making it up or had contrived to somehow deceive researchers and loved ones.
You have had 647 past lives, since you insist on being exact. This is your 648th. You were everything in them. A king, a queen, a serf. A teacher, a student, a master. A male, a female. A warrior, a pacifist. A hero, a coward. A killer, a savior. A sage, a fool. You have been all of it!
No, there is no such things as karmic debt, not in the sense that you mean in this question. A debt is something that must or should be repaid. You are not obligated to do anything.
Still, there are certain things that you want to do; choose to experience. And some of these choices hinge on, the desire for them has been created by, what you have experienced before.
That is as close as words can come to this thing you call karma.
If karma is the innate desire to be better, to be bigger, to evolve and to grow, and to look at past events and experiences as a measure of that, then, yes, karma does exist.
But it does not require anything. Nothing is ever required. You are, as always you have ever been, a being of free choice.