Proof of Purchase (also known as RITPOP or POP) is one of two co-ed a cappella groups at RIT. They perform mainly contemporary a cappella music.
POP was founded in the spring of 2009 by Rachel Rood (a member of Encore), and Craig Martek (a member of Surround Sound), who were frustrated with the lack of a mixed a cappella group on campus. Originally, the group was composed of members from the all-male and all-female groups until a rule limited individuals to being a part of only one a cappella group.
POP holds an annual spring concert known as ACAPOP, and has not competed in the ICCA's since 2014. The group's alumni song is the song Bright Lights by Matchbox Twenty.