The present work is concerned with an integration by parts formula for the P k -integral of De Sarkar and Das, and of the equivalent P k -integral of Bullen. The process involves a simpler and updated version of that for the Z^-i -integral of Bergin. If / is P k -(Zi t _ l )-integrable and G is of bounded fcth variation, then fG is P* -(Zi-i)-integrable.