How do I delete my purchase history

You cannot delete your purchase history. You can hide purchases: https://support.apple.com/en-us/HT201322

Ab3adisu Said:

"How do I delete my purchase history"

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Wait for Removal:

You'll have to wait until they are removed from the iTunes Library of Apple. Elsewise, they will stay there, hidden or not. Licensing will eventually expire, and it is then when Apple and the Studio or Developer decide to make it not longer accessible.