In genetics, a non-paternity event (also known as misattributed paternity, not parent expected, or NPE) occurs when an individual's presumed father is not in fact their biological father. This is a type of misattributed parentage experience (MPE) which can involve inaccurate assumptions made by an individual, their parents, or medical professionals. An NPE may result from sperm donation, closed adoption, heteropaternal superfecundation, promiscuity, paternity fraud, sexual assault, or medical errors during the process of assisted reproduction such as mixups during procedures such as in vitro fertilization and artificial insemination.[1] Where there is uncertainty, the most reliable technique for establishing paternity is through genetic testing. Currently, there are many direct-to-consumer companies that offer paternity testing. Internationally, June 27th is recognized as NPE Awareness Day. [2]