Catalyzes the final step of de novo phosphatidylcholine (PC) synthesis, i.e. the transfer of choline phosphate from CDP-choline to the free hydroxyl of a diacylglycerol (DAG), producing a PC. It thereby plays a central role in the formation and maintenance of vesicular membranes. . This is the function of CHPT1 (choline phosphotransferase 1, ENSG00000111666).